





I 






R>f.-y^-:':-''''r<'. ■ 



..fe-; 



' LIBRARY OF CONGRESS. 

Slielf.....H.?.. 



UNITED STATES OF AMERICA. 




International ^bntation ^txm 

EDITED BY 

WILLIAM T. HARRIS, A. M., LL. D. 



Volume IV. 



INTEKNATIONAL EDUCATION SERIES. 

Edited by W. T. Harris. 



It is proposed to publish, under the above title, a library for teachers 
and school managers, and text-books for normal classes. The aim will 
be to provide works of a useful practical character in the broadest sense. 

The following conspectus will show the ground to be covered by the 
series : 

I.— History of Education, (a:) Original systems as ex- 
pounded by their founders, (b.) Critical histories which set forth the 
customs of the past and point out their advantages and defects, explain- 
ing the grounds of their adoption, and also of their final disuse. 

II. — ^Educational Criticism, (a.) The noteworthy arraign- 
ments which educational reformers have put forth against existing sys- 
tems : these compose the classics of pedagogy, (b.) The critical histories 
above mentioned. 

HI.— Systematic Treatises on the Theory of Edu- 
cation, (a.) Works written from the historical standpoint; these, 
for the most part, show a tendency to justify the traditional course of 
study and to defend the prevailing methods of instruction, (b.) Works 
written from critical standpoints, and to a greater or less degree revolu- 
tionary in their tendency. 

rV.— The Art of Education, (a.) Works on instruction 
and discipline, and the practical details of the school-room, (b.) Works 
on the organization and supervision of schools. 

Practical insight into the educational methods in vogue can not be 
attained without a knowledge of the process by which they have come to 
be established. For this reason it is proposed to give special prominence 
to the history of the systems that have prevailed. 

Again, since history is incompetent to furnish the ideal of the future, 
it is necessary to devote large space to works of educational criticism. 
Criticism is the purifying process by which ideals are rendered clear and 
potent, so that progress becomes possible. 



History and criticism combined make possible a theory of the whole. 
For, with an ideal toward which the entire movement tends, and an ac- 
count of the phases that have appeared in time, the connected develop- 
ment of the whole can be shown, and all united into one system. 

Lastly, after the science, comes the practice. The art of education is 
treated in special works devoted to the devices and technical details use- 
ful in the school-room. 

It is believed that the teacher does not need authority so much as in- 
sight in matters of education. When he understands the theory of edu- 
cation and the history of its growth, and has matured his own point 
of view by careful study of the critical literature of education, then he is 
competent to select or invent such practical devices as are best adapted 
to his own wants. 

The series will contain works from European as well as American 
authors, and will be under the editorship of W. T. Harris, A. M., LL. D. 
The price for the volumes of the series will be |1.50 for the larger 
volumes, '75 cents for the smaller ones. 

Vol. I. The Philosophy of Education. By Johann Karl 

Friedrich Rosenkranz. 
Vol. II. A History of Education. By Prof. F. V. N. Painter, 

of Roanoke, Virginia. 

Vol. III. The Rise and Early Constitution of Univer- 
sities. With a Survey of Mediaeval Education. By S. S. Laurie, 
LL. D., Professor of the Institutes and History of Education in the 
University of Edinburgh. 



INTERNATIONAL EDUCATION SERIES -^ ^^ 



r 



0^ THE 



f 

YENTILATION AND WARMING OF 
SCHOOL BUILDINGS 




BY 

GILBERT b/mORRISON 

TEACHER OF PHYSICS AND CHEMISTRY IN KANSAS CITY IIIGII-SCIIOOL 




NEW YORK 
D. APPLETON AND COMPANY 

1887 



/y< 



v\&- 



Copyright, 1887, 
By D. APPLETON AND COMPANY. 



EDITOE'S PEEFACE. 



The practical character of the present volume will 
be at once manifest. Of the four departments of edu- 
cational literature — ^history, criticism, theory, and prac- 
tice — the last includes two classes of works : ^ 

1. Those that relate to instruction and discipline, 
and the details of teaching. Under this head come the 
arrangement of the course of study, the programme of 
daily work, the methods of teaching and discipline. 

2. Those that relate to the organization and super- 
vision of schools. Under this head we include works 
relating to school legislation, govei*ning boards, the 
building of school-houses, and the organization of a 
corps of teachers. 

Of these practical matters — practical because they 
relate to the application of theory to details, and imply 
the adaptation of means to ends — the question of the 
proper construction of school-houses is justly esteemed 
to be of great importance. The school-house is a per- 
manent affair. Other matters may be changed with less 
ceremony ; a building stands for two or more genera- 
tions. If it is faulty in its method of lighting, it will 
send out every seven years its quota of children all 



^ EDITOR'S PREFACE. 

affected more or less witli a tendency to wealmess of 
eyes, near-sigMedness, and to nervous dyspepsia and 
irritability of temper. If the ventilation has been de- 
fective, and a remedy has been sought by opening the 
windows, so as to admit cold air from the bottom, the 
seeds of future rheumatism and heart-disease have 
been sowed. If the warming has been imperfect, a 
long series of colds have weakened the lungs of pupils, 
and many cases of consumption resulted. 

The author truly remarks that " the greatest necessi- 
ties are often not felt as wants." Our early experience 
in a school-room that failed in these essential particu- 
lars has left on our minds, perhaps, in most cases, the 
impression that we did very well in the old-fashioned 
school-house. We were not able then to trace causes 
and effects in these matters on account of ignorance of 
hygiene. We have seen evil enough befall our com- 
panions in their life subsequent to the school, but it has 
not occurred to us to trace it to the exposure incident 
to improperly constructed school-buildings. 

It is believed that the present work furnishes a good 
text-book and book of reference to be used in normal 
institutes and normal schools. A short course of lessons 
or lectures will suffice to qualify a teacher to judge cor- 
rectly in matters of ventilation, and to act efficiently 
under all circumstances. When this is considered, it 
will be seen that every corps of teachers should be 
taught the theory and practice of warming and ven- 
tilating according to the experimental or investigating 
method. 

I have drawn up the following syllabus of topics 
and suggestions for a course of eight lessons, covering 



EDITOR'S PREFACE. vii 

the most important items of. tlie subject. I have also 
added a full analysis of the contents of the volume : 

Lesson I. — The general principles of hygiene as re- 
lated to ventilation. The necessity of pure air. Analy- 
sis of air. What impurities are found in the air of 
unventilated school-rooms. Pasteur's experiments. Ef- 
fect of breathing impure air — stupor, headaches, diseases 
of the lungs, dyspepsia, nervous affections, etc. (Chap- 
ters I, II, III). 

Lesson II. — How to test the purity of the air (Chap- 
ter lY). The proper degree of moisture in the air — 
73 per cent of saturation (Chapter III). How to test 
the degree of humidity (Appendix A, page 161, Glai- 
sher's factors). Amounts of moisture in th% out-door 
air at different temperatures (page 162) : at 80° Fahr., 
elastic force 1-023 ; at 70°, -733 ; at 50°, -361 ; at 32°, 
•181 ; at 20°, -108 ; at zero, -OM. If out-door air at a 
temperature of 20° Fahr. is heated in the school-room to 
70° without adding moisture to it, it is seven times as 
dry — that is to say, its capacity to absorb moisture has 
become seven times as great as before. Hence the dele- 
terious effect on the mucous membrane of the air-pas- 
sages and even on the skin of the body. 

Lesson HI. — The proper amount of light for a 
school-room. It should be hghted on two sides — from 
the rear of the pupils and from the left-hand side — not 
from the right-hand side, because of the shadow of the 
hand upon the paper when writing or drawing. The 
windows should extend to the top of the room, or at 
least as high as one half the width of the room, in order 
to hght sufficiently the pupils sitting farthest from the 
windows. Hence the room should not be too wide — 



yl[[ EDITOR'S PREFACE. 

not over 24 or 28 feet wlien the windows extend 14 feet 
above the floor. The length of the room may be 32 or 
34 feet. There should be three windows on the side and 
two at the end of the room. Double windows are very 
desirable for ventilation purposes (Chapter X), and for 
protection in very cold weather, when a current of 
chilled air falls down the surface of the window. If a 
room happens to be seated so that light comes from the 
right hand of the pupil, the desks may be changed so 
as to bring it from the left hand and rear. A school- 
building is ill constructed if its rooms have windows on 
one side only, unless the rooms are very narrow, and 
receive light solely from the north, as such rooms are 
sometimes constructed in Europe for advantages in 
drawing-lessons. Rooms on the soath, east, or west side 
of the building must exclude the direct rays of the sun 
during some portion of the day by curtains or shutters, 
and the consequence is that pupils sitting remote from 
the windows get too little light, unless thin white cur- 
tains are used and the windows are very large, and in 
height equal to two thirds the width of the room. 
Pupils sitting in twilight (the shutters being closed) 
become near-sighted in consequence of straining their 
eyes, or because they acquire a habit of holding the 
book too near the eyes. The correct form of school- 
building requires four rooms to each story — one on each 
corner. Two or three stories at most is enough, and a 
school-house should not stand nearer than 70 feet to 
another building, on account of the obstruction to light 
occasioned by it, especially to the rooms of the ground 
story. 

Lesson IY.— The amount of air required per pupil 



EDITOR'S PREFACE. ix 

— 2,000 feet per hour (Chapter Y). The average school- 
room, 28 X 34 X 14, with 60 pupils, furnishes fresh air 
enough to last 7 minutes. Methods of calculating 
the size of ventilators necessary, and the rapidity of the 
movement of the currents of air admitted through 
them (Chapter Y). The registers for the entrance of 
fresh air properly warmed should be distributed around 
the room. l!^atural ventilation depends on the fact that 
heated air is lighter and rises ; passing out of the top 
of the room, it sucks in fresh air through the inlets 
below (Chapters Y and YI). The inlets should be 
placed near the floor. Why ? (Chapter YII.) Size of 
flues admitting fresh air for 75 children — 10 square 
feet of total area. The foul-air flues shouM have an 
equal area. Importance of frequent cleaning of the 
foul-air shafts (Chapter YIII). 

Lesson Y. — Aspirating chimneys — what they are, 
and how large. The velocity of the column of air as- 
cending to be 7*7 feet per second. Discuss the two 
methods : (a) Drawing the foul air out of the bottom of 
the room into the aspirating chimney; (h) out of the 
top of the room (Chapter IX), The theory that im- 
pure air falls to the floor incorrect (Chapter YII). 
Method of drawing down pure air through a ventilating 
shaft, ^Necessity of heating the column of air in a foul- 
air shaft to secure its efiicient movement. The best 
plan to build large aspirating chimneys with iron smoke- 
stacks passing up through the center to heat the foul 
air. 

Lesson YI. — Yentilation by windows (Chapter X). 
Inconveniences of such ventilation—dust, smoke, waste 
of heat, cold drafts, etc. On account of defective plans 



X EDITOR'S PREFACE. 

for school-buildings, 99 per cent of the school-houses 
depend on windows and doors for ventilation. Always 
lower the windows from the top, except when the out- 
door temperature is above 80° Fahr., when they may 
be also raised from the bottom. In very cold or windy 
weather the windows should be lowered only one inch, 
or even less ; in moderate weather 12 inches, or even 
more. But all windows should be lowered alike, so as 
to move all the air in the room ; otherwise the ventila- 
tion will be v^y imperfect. If a window is opened 
too wide in cold weather, a chilly current pours in 
upon the necks and shoulders of children, and produces 
colds or rheumatism. If the windows are lowered only 
slightly, the cold fresh air moves down the surface of 
the wall and gets warmed somewhat in its descent by 
contact with the heated air. The devices of oblique 
boards fastened to the sash (Chapter X). The ejects 
of the wind when strong sometimes require the windows 
on one side to be nearly or quite closed. 

Lesson YII. — The most efficient means of ventilat- 
ing is a fan or blower (Chapter XII). It should be 
placed in the flues for fresh warm air (plenum move- 
ment), and not in the impure-air shaft (vacuum move- 
ment) (pages 79 and 80). The action of Kittenger's 
fan (pages 84-87 and Appendix C) ; of the Blackman 
fan (Appendix F). The method of calculating the 
efficiency of the aspirating chimney (Chapter XI and 
Appendix B). 

Lesson YIII. — The proper temperature of a room, 
70° Fahr. (Chapter XYI). General methods of warm- 
ing : conduction, i. e., by stove-pipes ; convection, i. e., 
by hot air from furnace or steam-coil ; radiation, i. e., 



EDITOR'S PREFACE. xi 

by open fire-place, standing coil, or stove. Importance 
of using large stoves or furnaces to avoid the neces- 
sity of overheating. The poisonous gases that escape 
through iron when heated to redness. Great advantage 
of radiant heat. Nearest to solar heat. Dr. Arnott's 
smokeless grate ; open fireplaces (Chapter XYII), The 
Ruttan system. Advantages and disadvantages of steam 
heating (Chapter XYIII). Direct radiation from steam- 
coils not good for the school-room, because it does not 
provide for moving the air of the room and for supply- 
ing fresh air ; warms the same air over and over ; difii- 
cult to provide for moistening the air ; needs a ventilat- 
"ing fan to render it efficient. Prof. Morrison's ideal 
plan for warming and ventilating ; distributes nis steam- 
coils underneath the floor with many small registers 
opening into the aisles of the school-room; foul air 
escapes at the top of the room into an aspirating chim- 
ney. 



CONTElsTTS. 



CHAP. PAOB 

I. — Needed Information 11 

II.— The Effects of Breathing Impure Air . . .17 

III.— The Air 24 

IV. — ^Examination op the Air . , . . ^. .31 

V. — Amount of Air Required 38 

VI. — General Principles of Ventilation .... 45 

VII. — Natural Ventilation 48 

Vni.— Inlets 51 

IX. — Regulating the Draft op Openings— The Wind. • 56 

X. — Ventilation by Windows 62 

XI. — Artificial Ventilation 70 

XII. — The Movement op the Air by Mechanical Means . 78 

XIII. — Air-Propellers , 82 

XIV. — Can the Plenum Movement be Afforded ? . . .90 

XV. — The Cost of Ventilation 97 

XVI.— Warming 104 

XVII. — Methods op Warming Ill 

XVIII.— Steam Heating 129 

XIX. — An Ideal Plan for Warming and Ventilating . . 144 

Appendix A. — Method op Testing the Humidity op the Air . 160 

B. — Aspirating Chimneys . , . . , .163 

C. — Rittenger's Fan (page 84) 166 

D. — Conducting Power op Material . . . .167 
E. — Radiating and Absorbing Power op Materials . 168 
F. — The Blackman Fan 169 

2 



AS"ALTSIS OF CONTEE'TS. 



Chapter I. Needed Information. — Advice plentiful (p. 11); questions 
to be answered regarding impure air — where found, its causes, its reme- 
dies ; most of the school-houses in the United States made without atten- 
tion to ventilation (p. 12); they depend on loose-fitting windows and 
doors for fresh air ; report of the commission appointed by congress on 
the public-school buildings in the District of Columbia (p. 13) ; systems 
of warming and ventilating in Boston, Denver, London, Vienna (p. 14) ; 
authorities consulted, R. S. Roeschlaub, Professors Parkes and Draper, 
Dr. de Chaumont, General Moran ; Dr. Neil Arnott (p. 15) and his la- 
bors (p. 16). 

Chapter II. Tlie Effects of Breathing Impure Air. — Symptoms caused 
by breathing impure air; stupor, headache, etc. (p. 17); not the carbonic 
dioxide, but the poisonous emanations from the skin and lungs (p. 18); 
bad air the cause of consumption ; authorities and statistics ; ventilation on 
ships ; New York Board of Health attributes 40 per cent of all deaths to 
breathing impure air (p. 21) ; effect of bad air on the work of the pupils 
and on their behavior (p. 22) ; financial waste in neglecting ventilation 
(p. 23). 

Chapter III. TTie Air. — Its composition : contains carbonic dioxide, 
even in its pure state, one part in 2,500 (p. 24). Its impurities: their di- 
lution in the air, diffusion ; ammonia the great supporter of microscopic 
animals, 200 forms of them found in the air ; Koch's and Pasteur's ex- 
periments (p. 26) ; street-dust near the ground contained 45 per cent of 
organic matter and 30 per cent at a height of 134 feet ; ground air 
unwholesome ; air poisoned by stoves and heating apparatus (p. 2*7). 
Humidity of the air: importance of supplying moisture to air heated 
in cold weather ; the dew-point ; 73 per cent of saturation the healthy 
standard ; statistics in hospitals, Washington and Boston ; shallow ves- 



xvi ANALYSIS OF CONTENTS. 

Bels of water on stoves and heating coils or hot-air ducts (p. 30) ; hy- 
grometers. 

Chapter IV, JSxamination of the Air. — Microscopic: Woulfe's bottles 
of pure distilled water connected by tubes and an air-pump (p. 32) ; cul- 
tivating solution. Cliemical: tests for carbonic dioxide, (pp. SS-SV). 

Chapter V. Amount of Air required. — One person evolves from 0*4 
to O'Y of a cubic foot of carbonic dioxide in an hour, and vitiates 2,000 
to 8,500 cubic feet of air per hour (p. 39) ; a school-room of average size 
(28 X 34 X 14 feet) would supply fresh air for less than seven minutes if 
there were no means of ventilation ; how to estimate the amount of air 
passing through a room (p. 40) ; air rushes into a vacuum with a velocity 
equal to what a body acquires in falling five miles ; it rushes into a 
room through a ventilator at a velocity equal to eight times the square root 
of the height of the exit orifice multiplied by the difference between the 
out-door and in-door temperatures in degrees Fahr. and divided by 491 (p. 
42) ; the anemometer can measure this ; insufficiency of ventilating 
registers and flues ordinarily in use (p. 44) ; air should be distributed to 
all parts of room through many registers. 

Chapter VI. General Principles of Ventilation. — Natural ventilation 
secured through the tendency of heated air to rise ; artificial ventilation 
secured by mechanical power ; illustration (p. 47). 

Chapter VII. Natural Ventilation. — Ventilators should be at the 
top of the room (p. 48) ; foul air rises with the heated air and is not to 
be found at the bottom of the room ; Mr. Leeds's experiment not conclu- 
sive (p. 50). 

Chapter VIII. Inlets. — Should be placed near the floor ; but avoid 
cold drafts ; warm the air before admitting it to the room ; downward 
currents in summer ; the inlets for air for 75 children should have an 
area of 10 square feet, and there should be the same area to the outlet 
flues, where there is a good aspirating chimney giving a velocity of 7'7 
feet per second ; the inlets should always be distributed round the room, 
so that free diffusion may occur ; the air furnished from a pure source 
and drawn from some distance above the ground (p. 54) ; shapes of cowls 
or conical caps to the shafts ; shafts frequently cleaned (p. 56). 

Chapter IX. Regulating the Draft of Openings — the Wind. — The ac- 
tion of the wind modifies the results obtained : increases the pressure of 
the air on the windward side of the room ; measurement of its amount 
(p. 57) ; classification of winds ; Dr. Amott's current-regulating air-valve 
(p. 58) ; admission of air at the top of the room ; McKinnell's circular 
tube (p. 61). 



ANALYSIS OF CONTENTS. xvii 

Chapter X. Ventilation by Windows. — Primary office of windows to 
admit light ; secondary office to ventilate ; the best ventilators in sum- 
mer ; admit dust and smoke ; deflection of currents admitted by means 
of oblique boards fastened to the' sash (p. 64); method of opening win- 
dows when the wind is blowing in order to secure fresh air without drafts 
(p. 66) ; the best results secured by double windows (p. 68). 

Chapter XI. Artificial Ventilation. — The vacuum movement — aspi- 
rating chimneys ; a column of heated air moves up the chimney and sucks 
up the foul air from the school-room through a register ; English House 
of Commons useis aspirating chimneys ; pure air drawn down one chim- 
ney and foul air drawn up another (p. 72); Montgolfier's formula for 
calculating the velocity of an upward current in a chimney (p. 74) ; ob- 
jection to carrying down the foul-air tubes to the furnace (p. 75) ; neces- 
sity of tall chimneys for ventilating ; efficiency of jets of steam in mov- 
ing air (p. 76) ; " absolute temperature " ; the distance above " absolute 
zero " which is — 459"4° Fahr. ; best to combine ventilating-flue with the 
smoke-chimney. • 

Chapter XII. Movement of the Air hy Mechanical Means. — Vacuum 
movement ; place in the foul-air duct an extracting fan or blower (p. 79) ; 
or let the blower force the fresh air into the room, a better method be- 
cause it fills the room with pure air, whereas the exhaust fan draws out 
the air from the room, but does not regulate the quality of the inflowing 
air ; hence impure air may come in through windows and doors as well as 
fresh air ; the " plenum movement " forces the fresh air into the room, 
the propeller being placed in the inlet duct ; the air forced into the room 
— perflation, blowing through — can be regulated perfectly in all cli- 
mates (p. 80) ; the plenum movement by far the best method of ven- 
tilating. 

Chapter XIII. Air-Propellers. — Revolving fans used for the most 
part ; Dr. Arnott's ventilating propeller (p. 83) ; Rittenger's fan (p. 84) ; 
Comb's fan (p. 87) ; Blackman's fan as modified by Hope Brothers ; pat- 
ent of Hendry and others (p. 88). 

Chapter XIV. Expense of the Plenum Movement. — Table of tem- 
peratures ; number of months that fire is required in twenty-eight cities (p. 
91) ; a thermal unit, the amount of heat required to raise the temperature 
of one pound of water 1° will raise 48 cubic feet of air 1° (p. 92) ; 180,000 
feet required in one hour in a school-room of 60 pupils ; hence, to raise 
that temperature 35°, the average amount for Chicago, 131,250 thermal 
units per hour are required ; the loss of heat through the walls exposed 
to external air, for 4 walls, 7,937 thermal units per hour (p. 93) ; loss 



Xviii ANALYSIS OF CONTENTS. 

through 6 windows, 3,572 thermal units, making total loss per hour, for 
fresh air and walls, 142,759 thermal units, requiring 18 pounds of coal per 
hour ; for seven months, a 10-room building would cost $512, if coal is 
$5 per ton (p. 94) ; this about the actual average cost of fuel in buildings 
that do not secure ventilation, but use the same air 30 to 60 minutes 
(p. 95) ; the heat is ordinarily wasted by windows, doors, too small heat- 
ing-surfaces, and the failure to introduce warm air at different points 
in the room (p. 96). 

Chapter XV. Cost of Ventilating Apparatus. — Cost of Aspirating 
Chimney (p. 97) ; to seciire a velocity of 8 feet per second for the air in 
the chimney requires 21 pounds of coal per hour, which is 3 pounds 
more than is required to heat the room, making the aspirating chimney 
expensive unless heated by the smoke-stack (p. 99); diagram of aspi- 
rating chimney heated by smoke-stack (p. 100) ; such chimneys usually 
made too small ; should furnish at least 6 square feet of sectional area 
for each room, and for 14 rooms be 9 feet square (p. 101) ; cost of the 
plenum movement {'^. 102); the Rittenger fan requires one horse-power 
for each room, and 5 to 8 pounds of coal per hour ; the Blackman fan 
and the Hope water-motor fan much cheaper (p. 102); advantages of 
plenum movement — acts in all weathers and establishes current of fresh 
air independent of windows or accidental openings (p. 103). 

Chapter XVI. Warming, — Temperature of the room should be 70' 
for school-rooms (p. 104) ; with sluggish circulation of blood, a person 
needs a higher temperature; transmission of heat by conduction, con- 
vection, and radiation (p. 105) ; heaters should be large, so as to avoid 
overheating of surface ; poisonous gases escape from a red-hot stove ; 
stoves, steam-pipes, and stove-pipes heat by conduction ; an open fire in 
a grate heats by radiation ; radiant heat the healthiest (p. 106) ; spec- 
trum analysis (p. 107) ; sanitary effects of radiant heat — it warms the 
body without heating the air (p. 108) ; but warms only one side at a time 
(109) ; convection is the method of conveying heat by the movement of 
currents of warm air (p. 110). 

Chapter XVII. Methods of Warming. — The open fireplace in the 
City of London High-School (p. Ill) ; Dr. Arnott's smokeless grate (112); 
description of it (p. 113); would use 4 pounds of coal per hour for a 
school-room 30 x 30 x 14 feet ; Boyd's open fireplace provides for ad- 
mission of cold fresh air and warming it (p. 114); if stoves are used, 
large ones should be selected, so as to avoid overheating, and should be 
lined with fire-brick— long smoke-pipe, extending round the room, so as 
to economize the heat (p. 116); stoves the cheapest means of warming 



ANALYSIS OF CONTENTS. xix 

known; Dr. Arnott's self-regulating stove (p. 117); smoke consumed by 
it ; common stove with a drum (p. 119) ; improved stoves by A. M. Hicks 
and A. Dishman, of Kentucky ; Baltimore Heater (p. 120) ; the Rattan 
system discussed ; Smead's invention for mixing hot and cold fresh air 
(p. 122) ; escape of foul air at the bottom of the room in the Ruttan sys- 
tem (p. 125) ; necessity of strong draft to secure proper ventilation by 
this system; waste of heat in the top of room (p. 126); necessity of 
cleansing foul-air passages ; mistakes or neglect of builders. 

Chapter XVIII. Steam- Heating. — English House of Commons heated 
by means of furnace- warmed air, on a modified plan of Dr. Reid (p. 129) ; 
hot-air chamber beneath the floor, foul-air flues at the top of the room ; 
amount of heat conveyed by steam ; experiment to prove the ratio of 
latent heat in water to sensible heat (p. 132) ; upon condensation, all the 
latent heat of steam becomes sensible heat ; Mr. Holly's method of in- 
sulating steam-pipes; 1,600 feet of 3-inch pipe lost by radiation only 2\ 
per cent (p. 134) ; one pound of coal converts 9 pounds of water into 
steam, and realizes 8,640 thermal units ; hence 16'66 pinnds of coal 
necessary to supply a room for an hour, being 2 pounds less than by 
furnace heat (p. 136); direct radiation by steam-coils condemned, unless 
ventilation is provided ; plan of room with proper ventilation (p. 138) ; 
Washington school-buildings heated by direct radiation and without ven- 
tilation (p. 139); steam-pipes extending round the sides of the room 
near the floor (p. 140) ; heating of same air over and over ; indirect ra- 
diation by steam-coils placed beneath the floor, and fresh air warmed by 
passing over them and into the school-room ; needs a good aspirating 
chimney or a ventilating fan ; steam radiators placed under windows, in 
order to counteract cold currents, or near the inside walls of the room, to 
save loss of heat (p. 143) ; but the heat ascends to the top of the room, 
and is not distributed properly. 

Chapter XIX. Ideal Plan for Warming and Ventilating. — The feet 
should be kept warmer than the head (p. 145) ; plan described for warm- 
ing and distributing fresh air through the floor (p. 146) ; chimney 8 feet 
square, with foul-air flues opening into it from the tops of rooms ; fresh- 
air shaft bringing down the air from the top of the building ; registers 
along the aisles by the side of the desks (p. 148) ; method of cleansing 
the registers (p. 150) ; method of creating a draft iu warm weather 
(p. 152); three pipes to regulate the amount of heat supplied (p. 153); 
double joists in the floor necessary for this plan ; sufficient ventilation 
without resort to the windows ; plan of 16-room school-house, two stories 
in height (p. 156) ; chimneys placed between the rooms ; iron ladders inside 



XX ANALYSIS OF CONTENTS. 

the chimneys (p. 15*7) ; one half size for 8-room buildings plan for a 6- 
or 12-room building (p. 158). 

APPENDIX. 

A. Mr. Glaisher's observations on dry- and wet-bulb thermometers ; 
his factors for testing the moisture of the air (p. 161). 

B. Simple form of aspirating chimney (p. 164) ; formulae for calcu- 
lating its efficiency. 

C. Formulae for constructing Rittenger's fan (see pp. 84-87). 

D. Conducting powers of materials ; copper more than twice the con- 
ducting power of iron and zinc, and nearly five times that of lead ; 19 
times as great conducting power as marble ; 100 times that of brick ; 
300 times that of oak. 

E. Radiating and absorbing power of bodies ; silver lowest and oil 
highest (p. 168). 

F. The Blackman fan with author's improvements; drawings show- 
ing formation of the blades (p. 110) ; description of devices to prevent 
back-flow of air (p. 171). 



PEEFACE. 



The following pages are not intended to " fill a long- 
felt want." The greatest necessities are often not felt 
as wants. If an individual suffers from a cause which 
is unknown to him, he feels no want, necessarily, to re- 
move that cause. If a man sickens from a want of pure 
air, without knowing the cause of his ailment, he never 
longs for a more salubrious atmosphere as a cure. 

I am fully convinced that people are prematurely 
dying by thousands simply from a lack of correct and 
positive convictions concerning impure air ; for, when 
the true nature of a danger is fully appreciated, the 
requisite means to avert it will generally be found. 

Every teacher, or other person who works in a viti- 
ated atmosphere, has doubtless noticed the peculiarly ex- 
hilarating effect of going into the open air after a day's 
indoor confinement. My own experience in this respect 
is so marked that I seldom step from a crowded room 
into the open air without reflecting on the nature of that 
invisible cause which made possible a change so sudden 
and so marked. This reflection is always followed by 
the mental query : Can not this great difference between 
the qualities of outdoor and indoor air be remedied? 



xxii PREFACE. 



THs experience, together with almost daily observation 
of the attempts of builders to ventilate houses, wherein 
the simplest physical laws are commonly ignored, has 
led to the writing of these pages. 

The work is confined to the consideration of school- 
buildings for three reasons : 1. I am better acquainted 
with the needs and present condition of school-houses 
than of any other class of buildings. 2. These build- 
ings, because of crowded occupancy during successive 
days, are most in need of perfect ventilation. 3. 
Knowledge of the correct principles of school-house 
ventilation is knowledge equally applicable to all build- 
ings, as the same principles underly all. 

Correct theories and their successful application to 
the arts of life can not be conceived and executed in 
a day. Our knowledge of warming and ventilating 
is a growth to which each generation has probably in 
some measure contributed. Any contribution, there- 
fore, to be of value, must be made in the full light of 
what has preceded it. In preparation for the present 
task, therefore, I have carefully read the writings of 
the following authors who have contributed to this sub- 
ject : Parkes, de Chaumont, Kitchie, Hood, Morin, Ed- 
wards, Eassie, Eeid, Arnott, Tomlinson, Billings, Galton, 
Leeds, Schumann, Baldwin, Draper, and Lincoln. I 
also procured from the United States Patent OjBfice 
drawings and specifications of thirty different ventilat- 
ing appliances which have from time to thne been pa- 
tented. Whatever the Bureau of Education has fur- 
nished has also been read. The best, therefore, that has 
been thought or done on this subject has been carefully 
studied, and whatever is valuable has become assimi- 



PREFACE. xxiii 

lated into this work, in so far as it informed, invigorated, 
and corrected my own thought. 

The chapter on window-ventilation will, I think, be 
useful to teachers. While windows at best can furnish 
only partial and imperfect ventilation, it is only by their 
skillful management that even so nmch may be real- 
ized from them. 

The discussion in this book of some of the modem 
systems of warming and ventilating is made from an in- 
dependent and 4inbiased study of their merits, and with- 
out any interest in advertising either their excellences 
or their defects. 

The ideal plan described and illustrated iji the last 
chapter was not conceived until nearly all preceding it 
had been written. It may be regarded, therefore, as the 
result of a long and exclusive application to the subject. 

For valuable suggestions, I wish to acknowledge my 
obligations to Prof. Wm. Jones, Professor of Chemistry 
in the Kansas City Medical College, for reading the 
manuscripts on the chemical examination of the air ; to 
Prof. L. Wiener, of the Kansas City High School, for 
reading the mathematical discussion of ventilating 
fans ; and to Prof. J. M. Greenwood, Superintendent 
of Kansas City Schools, for reading the same and other 
portions of the manuscripts. 

G. B. Morrison. 

Kansas City^ Mo. 



VEI^TILATION AND WARMING OF 
SCHOOL-BUILDINGS. 



CHAPTEE I. 

ITEEDED IKFORMATIOIT. 

Advice regarding 'Afresh air" has not been lacking 
in amount. Even the most ignorant have some indefinite 
notion that there is such a thing as ^^bad air," and that 
it is not good to breathe it. Teachers of hygiene pro- 
claim to pupils the virtues of pure air, shut up in school- 
houses where it is impossible to get it. Physicians 
advise their patients to take fresh air, and this by going 
out of doors, thus tacitly realizing that it can not be 
found indoors. Preachers in churches, where deadly 
gases from the lungs and poisonous organic emanations 
from the skin are imprisoned from week to week, em- 
phasize the importance of properly preserving the physi- 
cal body. There is a universal recognition that it is bad 
to breathe impure air ; there is an ignorance no less uni- 
versal of the conditions of how to avoid it. When the 
nature and composition of a deadly drug are known and 
marked ^'Poison," it is properly avoided. In the next 
section we shall see that much of the air we breathe 
should be labeled with skull and cross-bones. 

Where is the impure air ? What makes it impure ? 
8 



12 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

What are the nature and amount of the impurities ? 
These are important questions which, among the edu- 
cated, are tolerably well known. But when these im- 
purities exist in an occupied room, how are they to be 
eliminated and replaced by pure air of the proper tem- 
perature ? These are questions which are no less im- 
portant ; but they are questions which are seldom an- 
swered. How to know where impurities exist ; how to 
expel them as fast a3 formed, and supply their place 
with the pure, life-giving element, is a problem second 
in usefulness to none other. Of the difficulty of the 
problem we have ample evidence in the fact that it has 
been but partially solved, and in general practice almost 
wholly ignored. True, we hear men talk of " good 
ventilation" and *^poor ventilation," but how little this 
generally means we hope, at least partially, to show in 
the pages of this little book. 

Of the lack of definite information on this all-impor- 
tant subject we have abundant evidence. We often hear 
tlie questions: "What is the best way to ventilate a 
school-room ? Where should the foul air escape ? Where 
should the pure air be admitted?" These questions, 
among the first to be met in ventilation, show that even 
the first principles of matter and its properties are not 
pommonly applied to the gas we call air. 

The school-houses throughout the United States, while 
they are elegant, tasteful, and costly, are in the main de- 
ficient in their sanitary requirement of warming and ven- 
tilating. Whoever may be disposed to doubt the truth 
of this statement has but to visit the nearest school-house. 
Probably in nine tenths of all the school-houses in this 
country ventilation has been ignored altogether, leaving 
that important function to be performed by the doors 
and windows, But ventilation should ]be independent of 



NEEDED INFORMATION. 13 

doors and windows, which are primarily intended for 
other purposes. How many school -rooms in the land 
could maintain a school with doors and windows made 
air-tight ? Probably very few, and in the majority suffo- 
cation would result in less than thirty minutes ! It is a 
sad travesty on our school architecture that we owe our 
lives to the mistakes of carpentry, which mistakes are 
usually sufficiently ample to supply, in a crude, unwhole- 
some, and unsatisfactory way, the deficiencies of direct 
ventilation. 

This want of sufficient and definite information re- 
garding the ventilation of school-houses is not peculiar to 
any locality ; it is wide-spread and general. Even the 
District of Columbia, which is under the direct control 
of the Central Government, experiences the embarrass- 
ments which this all-important but vexed problem pre- 
sents. By a resolution of the House of Eepresentatives, 
dated February 20, 1882, a commission was appointed for 
the purpose of investigating the public-school buildings 
of the District of Columbia. A few quotations from the 
report of this committee will be to the point : *' The 
principal defect, from a sanitary point of view, in all these 
buildings is in regard to the fresh-air supply, which is en- 
tirely insufficient. The method adopted for this purpose 
is to admit the air through a perforated plate placed be- 
neath the sills of four windows in each room. Having 
passed through this plate, the air is supposed to pass 
downward through a narrow slit in or behind the wall, 
and to enter the room at a level with the floor and then 
pass up through a steam radiator which is placed against 
the window. The sum of the clear opening in the exter- 
nal plate of each window is from twenty-two to twenty- 
five square inches, so that the area of clear opening for 
the supply of pure air to the room is from eighty-eight to 



14 VENTILATION AND WARMING OF SCnOOL-BUILDINGS. 

one hundred square inches, giving an average of about 
two thirds of one square foot. When it is remembered 
that this is intended to supply fresh air for sixty children, 
each of whom should have as a minimum thirty cubic 
feet of air per minute, it will be seen that it is simply im- 
possible to obtain such a supply through the openings 
provided, which in fact will hardly furnish five cubic feet 
per minute per pupil." 

This report has not been quoted from to show the best 
that has been done in school-house ventilation, but rather 
what may be considered a fair representation of the aver- 
age state of affairs throughout the country. 

Something toward a rational system of warming and 
ventilating is said to have been accomplished at the Bos- 
ton High School ; also at Denver, in this country ; but 
more especially at the City of London High School, and 
the High School of Vienna, in Europe. 

When first contemplating the preparation of this vol- 
ume, I thought to write to several superintendents, in 
cities having a reputation for good school-houses, asking 
them to furnish me with descriptions of their system of 
heating and ventilating, that I might use them as a feat- 
ure of my work, incorporating them as models of the best 
modern types of school-house architecture. Some an- 
swered by sending a pamphlet in which ventilation is bare- 
ly referred to ; others by letter ; but the average signifi- 
cance of them all may be given in the exact words of 
one of them : '^ Our high school is a showy building on 
the outside, but it is not well warmed and ventilated." 

Few things are more needed than a systematic dissemi- 
nation of the best that is known of proper methods of ven- 
tilation, as well as stimuli to investigate the underlying 
principles. A subject so vital to the health and safety of 
the growing generation should be investigated by every 



NEEDED INFORMATION. 25 

teacher of physics, and the known laws of fluid pressure 
and motion be directly applied and taught. It should be 
a theme for the educated i^hysician, whose duty it is not 
only to cure disease but to prevent it. It should be the 
duty of every school-house architect not only to make the 
best practical use of the best that is known on the sub- 
ject, but to furnish annual reports of the conditions of 
the school-buildings, a description of each buildiug, the 
cost, method of warming and ventilatiug, the air-space 
for each pupil, the percentage of heat which is utilized 
in the consumption of fuel, etc. The people's right to 
information on any subject should be measured by the 
value and indispensableness of the information ; and 
surely nothing is of more universal importance than the 
air we breathe, affecting as it does our health, life, and 
future condition. 

The importance of this kind of information has not 
been wholly ignored. The Denver report of 1883 con- 
tains a chai^ter on school architecture in which the stu- 
dious labors of the architect, Mr. Eobert S. Eoeschlaub, 
are laid down for the consideration and enlightenment of 
the public. Many valuable hints on the general subject 
of warming and ventilating have been given by different 
writers on hygiene, among whom may be mentioned Pro- 
fessors Parkes and Draper. From a purely scientific stand- 
point probably the most has been done by Dr. de Chau- 
mont. The governments of France and England have 
contributed much knowledge on the subject by health 
commissions appointed to investigate the sanitary condi- 
tions of barracks occupied by soldiers ; the reports of 
General Moran being especially valuable. But it is to 
Dr. Neil Arnott, the famous Scotch educator and physi- 
cian, that humanity owes most for practical knowledge 
on warming and ventilating. Deeply versed in physics, 



le VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

being tlie aiitlior of a yaluable text-book on that sub- 
ject, he understood the principles and laws under- 
lying the subject. A physician, being one of the most 
eminent in the realm, he well understood the vitiating 
effects of impure air. A practical inventor, he put his 
theories in practice by inventing many heating and venti- 
lating appliances, among which may be mentioned the 
Arnott stove, the smokeless grate, and an automatic 
valve for admitting fresh air to fire-places. A philan- 
thropist, he gave his thoughts and inventions to the 
world free of charge, refraining always from securing 
patents and coj^yrights. He did not overlook the needs 
of the schools; he applied his principles to the "Field 
Lane Eagged School " — by a method to be noticed here- 
after — with excellent results. 

A little reflection will answer why a teacher should 
undertake to contribute to this important subject. The 
heaviest blows in any cause have always been struck in 
self-defense. The teacher is defending himself in en- 
deavoring to better the atmospheric condition of the 
school-room where he spends the most of his active life. 
Whatever may be said in the defense of children who are 
submitted to the contaminating influences of an impure 
atmosphere, the same may be urged with tenfold em- 
phasis in the defense of teachers ; for while the pupil's 
school life lasts only a few years, the teacher's term is a 
life-time. While it is the duty and desire of all good 
men to help others, the sternest efforts are always made 
in the direction of self-preservation, which, if successful, 
will increase the capacity to help others. I offer no 
apology, therefore, for contributing to a subject in which 
all humanity, and especially all teachers, are so deeply 
interested. 



THE EFFECTS OF BREATHING IMPURE AIR. 17 

CHAPTER 11. 

THE EFFECTS OF BREATHING IMPURE AIR. 

NoKE except he who has given special study to the 
facts begins to realize the injurious effects of breath- 
ing impure air. Every one knows that a disagreeable 
feeling accompanies the breathing of impure air ; that a 
feeling of stupor, inactivity, drowsiness, and sometimes 
nausea, headache, and vertigo, result directly from the 
occupancy of ill-ventilated rooms. These sensations are 
temporary, and are experienced only while the cause is 
active, and usually the only thought is to temporarily 
relieve the inconvenience by a recess or a break for fresh 
air. Seldom do persons reflect on the ulterior effects of 
these violations of Nature's laws, and when the outer 
air is reached, and long draughts of the pure element 
relieve the depressed sensations, and send the invigorat- 
ing oxygenated life-blood current coursing through the 
system, raising the spirits and clearing the brain, their 
reflection usually end with relief, and, when more or less 
resuscitated and rescued from the fatal stupor (I use the 
phrase advisedly), the unsuspecting victims crawl back 
into their ^^ Black Holes," again to fill the system with 
gaseous poisons, thinking of it only as an unjDleasant 
duty, the immediate endurance of which will bring sub- 
sequent freedom and relief. But this is a great mistake ; 
the temporary suffering consequent on the act of breath- 
ing vitiated air is but a small part of the objection to 
be urged against it. The principal charge against the 
breathing of impure air is that it sows the seeds of dis- 
ease and death, the length of time in which the subject 
will succumb being in proportion to his strength and 
power of endurance. 



18 VEJfTILATING AND WARMING OF SCHOOL-BUILDINGS. 

No subject has been more carefully and intelligently 
studied than the direct and ultimate effects of impure air 
on the human system, and on no subject is there more 
unanimity of competent opinion. Besides the general 
debilitating and weakening effects, which render the sys- 
tem susceptible to infectious diseases, breathing impure 
air is believed by the best authorities to be a direct 
cause of phthisis (consumption) and its accompanying 
diseases — catarrh, bronchitis, pneumonia, and many oth- 
ers. 

The individual effects of breathing separately the 
foreign gases usually found in the atmosphere need not 
be considered here, but it is their combined effect, com- 
bining as they do with organic emanations from the skin 
and lungs, that chiefly concerns us in considering the 
effect of impure air made so by respiration. Carbon- 
ic dioxide, 00^, is commonly considered the poisonous 
substance in the atmosphere ; this is in the main untrue, 
for moderately large quantities, when pure and mixed 
with air, can be breathed with impunity. CO2, by its 
inability to support life, will produce asphyxia by shut- 
ting out the needed oxygen, but it can not be regarded 
as a poison. Substantially the same conclusions have 
been reached by Demarquay, Angus Smith, W. Miiller, 
Eulenberg, and Hirt, all of Vfhom have made close in- 
vestigations. It is when mixed with the organic emana- 
tions from the skin and lungs that the poisonous quality 
seems to be present ; and Gavarret and Hammond found 
that the organic matter when taken alone is "highly 
poisonous." It seems, therefore, that the principal poi- 
soning agents in impure air are organic. Nevertheless, 
the amount of COg in the air is highly important, for its 
presence is a very good index of the amount of the organic 
impurities, and to measure the percentage of CO3 is indi- 



THE EFFECTS OF BREATHIXG IMPURE AIR. I9 

rectly to measure the degree of vitiation of the air. (See 
Examination of the Air.) 

On the disease-producing effects of air rendered im- 
pure hy respiration we have a host of authorities. The 
following statistics are from the English sanitary record, 
given by Ransom, showing the comparative death-rate 
from pulmonary diseases in different localities where the 
relative impurities are known to vary in about the same 
ratio as is shown in the death-rate. For all England, 
1865-'76, 3-54 ; for Salford, 5-12 ; Manchester, 7*7 ; West- 
moreland, one of the healthiest counties, 2*27; North 
Wales, 2 'SI. It is, of course, not to be forgotten that other 
causes, such as intemperance, insufficient and improper 
food, sedentary pursuits, etc., also conspire in tl^se unfa- 
vorable localities to produce the final result. *^But," as 
Dr. Parkes remarks, *^ allowing the fullest effect to all 
other agencies, there is no doubt that the breathing of the 
vitiated atmosphere of respiration has a most injurious 
effect on the health." Consumption is commonly attrib- 
uted to sudden and undue exposure to wet and cold, want 
of sufficient food, clothing, etc., but Baudelocque says that 
** impure air is the great cause of consumption, and that 
hereditary predisposition, un cleanliness, want of clothing, 
bad food, cold and humid air, are by themselves non- 
effective." The following paragraph from Parkes's ** Hy- 
giene " I copy for the weight of authority in the eminent 
names mentioned therein : 

" Carmichael, in his work on ^ Scrofula ' (1810), gives 
some most striking instances where impure air, bad diet, 
and deficient exercise concurred together to produce a 
most formidable mortality from phthisis. In one in- 
stance in the Dublin House of Industry, where scrofula 
was formerly so common as to be thought contagious, 
there were in one ward, sixty feet long by eighteen feet 



20 VENTILATION AND WARMING OF SCnOOL-BUILDINGS. 

wide, thirty-eiglit beds, eacli containing four children : 
the atmosphere was so bad that in the morning the air of 
the ward was unendurable. In some of the schools exam- 
ined by Oarmichael the diet was excellent, and the only 
causes for the excessive phthisis were the foul air and the 
want of exercise. This was the case also in the house and 
school examined by Neil Arnott in 1832. Lepelletier 
also records some good evidence. Prof. Alison, of Edin- 
burgh, and Sir James Clark, in his invaluable work, lay 
great stress on it. Neil Arnott, Toynbee, Guy, and others, 
brought forward some striking examples before the Health 
of Towns Commission. Dr. Henry MacCormac has in- 
sisted with great cogency on this mode of origin of phthi- 
sis ; and Dr. Greenhow also enumerates this cause as oc- 
cupying a prominent place." 

Gavin Milroy, in his pamphlet on the *^ Health of the 
Eoyal Navy," expresses his belief that the extraordinary 
mortality from consumption on some of the ships was due 
mainly to im])roper ventilation. The writer on the sub- 
ject of ^^Consumption" in ''Chambers's Encycloi38edia" 
says : ''Among the determining causes of consumption 
in large populations the best ascertained are those con- 
nected with overcrowding and had ventilation.^'^ Lan- 
genbeck, an eminent anatomist, says that the prime cause 
of consumption is breathing impure air. 

Impure air is also believed by the best authorities to 
be one of the principal causes of epidemics. Dr. Carpen- 
ter, than whom there is no abler authority, says : *'It is 
impossible for any one who carefully examines the evi- 
dence to hesitate for a moment" in the conclusion that the 
fatality of epidemics is almost invariably in precise pro- 
portion to the degree in which an impure atmosjDhere has 
been habitually respired." The Board of Health of New 
York conclude that forty per cent of all deatlis are caused 



THE EFFECTS OF BREATHING IMPURE AIR. 21 

by breathing impure air. In view of such alarming facts, 
this same board declares : *' Viewing the causes of pre- 
ventable diseases, and their fatal results, we unhesitatingly 
state that the first sanitary want in New York and Brook- 
lyn is ve7itilatio7i." Direct experiment described in an- 
other place, no less than the direct evidence of the senses, 
proves that the air in our school-rooms is impure in al- 
most all cases, and in a majority of them to a degree far 
beyond the danger line. 

In view of these facts, and the results as proved by 
the authorities above cited, why is it regarded by the 
public with such indifference ? When a school-house is 
blown down by a hurricane, killing and maiming a score 
of children, it is justly regarded as a great calamity ; a 
vacation is given to quiet the excited fears of parents and 
children ; investigating committees are appointed to lo- 
cate the responsibility, and the faces of the whole pop- 
ulace are blanched with apprehension. Why is this? 
Why does the intelligent parent send his child to a 
school-room poorly ventilated and crowded with chil- 
dren, some of whom are breathing into a stagnant air 
the germs of disease and death, while others, from un- 
washed bodies, are delivering into it their deadly ema- 
nations, and all without a protest on the part of those 
even who provide proper hygienic conditions at home ? 
It is because the effects of the one are immediate, occupy 
little time, the number killed can be actually counted, 
and the exact magnitude of the calamity estimated all at 
once. In the other case the process is slower, but of far 
greater extent ; the actual results are by the general pub- 
lic less definitely known, and custom and attention to 
other matters divert the attention, and the deadly de- 
struction of the innocents by impure air goes on silently, 
constantly, and powerfully. W^hile noisy demonstrations 



22 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

like that of the cyclone attract attention, and inspire fear 
and terror, it is in the silent forces that the danger lies. 
Nature's most destructive forces, as well as her strongest 
constructive ones, are silent in their operations ; bat when 
Science detects a silent, insidious enemy to human welfare, 
it is not only our duty to assume an attitude of self-defense 
and self-protection, but it should be regarded as folly 
not to do so. Could the real effects of breathing impure 
air be fully realized by the public, and the actual amount 
that is really breathed be definitely known, such a knowl- 
edge would constitute a most powerful stimulus toward 
solving the problem of ventilation, as well as create a dis- 
position to provide the means necessary thereto. 

The effects of breathing impure air thus far consid- 
ered are pathological, but it has its pedagogical and eco- 
nomical aspects. Every observing teacher knows the 
immediate relation between the vitiated air in the school- 
room and the work he wishes the pupils to perform. 
Much of the disappointment of poor lessons and the tend- 
ency to disorder are due directly to this cause. The 
brain unsupplied with a proper amount of pure blood re- 
fuses to act, and the will is powerless to arouse the flag- 
ging energies ; the general feeling of discomfort, dissatis- 
faction, and unrest which always accompanies a bad state 
of the blood breeds most of the school-room squabbles, 
antagonism, misunderstanding, and dislike which are 
wont to occur between teacher and pupil. The pupil 
apparently at variance with his teacher is really at war 
with his own feelings, caused by an impure and stagnated 
condition of the blood. The teacher who sometimes 
thinks the pupils are all conspiring against him, and who, 
with dizzy and clouded brain, says the wrong thing at 
the wrong time, is really struggling with the poison which, 
on account of his long seclusion from the cheerful air, has 



THE EFFECTS OF BREATHING IMPURE AIR. 23 

taken possession of him. Teachers observe how much 
more satisfactory is the work of the first hour of the day 
than that of any subsequent hour ; this is not because of 
weariness of the pupils, it is because they are made stupid 
and obtuse, and the teachers made uneasy and fretful, by 
the accumulating poisons from skin and lungs. 

From an economical standpoint it would, of course, 
be impossible to estimate the financial waste of breathing 
impure air, but it can not but be enormous. In a com- 
fortable atmosphere of proper temperature and purity 
as much mental labor can be accomplished in one hour 
as can be accomplished in six in an atmosphere rendered 
impure by respiration. This is, of course, but a random 
estimate, but I am quite sure that whatever of error it 
contains is on the side of underestimating the deteriorat- 
ing influences of impure air rather than of overestimating 
the value of pure air. If, then, we suppose perfect ven- 
tilation possible, and that this estimate is not overdrawn, 
the conclusion follows that in those school-rooms where 
ventilation is imperfect and the air impure six sevenths 
of the money expended to educate a child is wasted. 
Doubtless this will appear to some as an exaggerated 
statement ; but, if we accept the premises (and this will 
readily be done by all who have tried to think in an un- 
ventilated room), the conclusion is inevitable. This con- 
clusion supposes that perfect ventihition costs no more 
than imperfect or no ventilation ; while this is not strictly 
true, the difference is insignificant when compared with 
the loss we are considering. In any discussion of the 
feasibility of incurring the additional expense of the most 
perfect ventilation, this loss occasioned by the want of 
such ventilation must not be ignored. 



24 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

CHAPTER III, 

THE AIK. 

Tlie Composition of the Air, — The gaseous enyelope 
which surrounds the earth, and which we call air, is one 
of the conditions of animal and plant existence. It is 
evident, therefore, that a definite knowledge of its com- 
position and properties is all important. In order to in- 
Testigate the abnormal conditions which often prevail, 
with a view to correcting them, we must first know the 
normal conditions. 

The air is composed mainly of two gases, oxygen and 
nitrogen, in the proportion of about 21 of the former to 
79 of the latter. The following, from Parkes's " Hygiene," 
is probably as exact as has yet been ascertained : 

Oxygen 209-6 per 1,000 volumes. 

Nitrogen 790*0 " '' " 

Carbonic dioxide (CO2) . , . , '4: " '' " 

Watery vapor Varies with the temperature. 

Ammonia Trace. 

Organic matter , 



Variable. 



Ozone. , 

Salts of sodium 

Other mineral substances. 

Pure air is usually considered as consisting exclusively 
of oxygen and nitrogen, all other elements existing as 
impurities in it. But as the air is a mixture of the 
constituents, and not a chemical compound, and as the 
proportion of these elements is yariable, it seems more 
reasonable to regard as the true normal air that propor- 
tion of the different elements which best conserves the 
ordinary uses of air in the support of plant and animal 
life. Without the CO2, small though it be, the air would 



THE AIR. 25 

be wanting in that constituent which plants most need ; 
and a certain amount of watery vapor is equally indis- 
pensable for the use of animals. It seems, therefore, that 
CO3 and watery vapor, in the proportions above men- 
tioned,* are really as truly constituents of air as oxygen 
and nitrogen. 

Impurities in the Air. — There are many substances, in 
many forms and from various sources, constantly passing 
into the air, tending to make it impure and unfit for 
respiration. Of these, those which more especially con- 
cern us in consideration of the condition of our school- 
houses are vapors and gases from the skin and lungs, 
principally CO2 and vapor of water ; solid particles of 
scaly epithelium from the skin, fibers of cotton, wool, 
etc., bits of hair, wood, coal, chalk-dust, and many other 
things which have a tendency to enter the blood through 
the delicate air-cells in the lungs, if gaseous, and to lodge 
in the air-passages or be drawn into the lungs if solid, 
there to irritate by their presence, and poison the system 
by their decay. 

But Nature, when not hampered by man, has provided 
a compensation for this poisoning process by a counter 
process of purification. The winds scatter the impurities, 
diluting them with large quantities of air, oxidizing them 
into simple compounds, and rendering them harmless. 
The tendency which gases have to diffuse causes poison- 
ous substances to be rapidly diluted, to such a degree as 
to destroy their destructive power. It is evident, then, 
that wherever the contaminating process is active there 
also should the purifying process be active. Wherever 
an unusual amount of unwholesome matter is being 

* The exact amount of watery vapor in the air which best serves the 
purposes of respiration is not definitely known, but, as far as ascertained, 
it is considered to be about seventy per cent of saturation. 
2 



26 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

evolved, there especially should the purifying conditions 
be present ; air in such places, to remain pure, must be 
changed in rapid succession, in order that dilution, diffu- 
sion, and oxidation may fulfill their legitimate functions. 
In a school-room the contaminating process can not but 
be rapid, and wherever ample provision is not made for 
rapidly changing the air of the room a dangerous con- 
dition of affairs is sure to exist. 

In addition to the inorganic substance suspended in 
the air there is a vast number of organized bodies. While 
some of these organisms are to be found in pure air, they 
are vastly more numerous in impure air, and more espe- 
cially in that impure air made so by animals. Ammonia 
seems to be the great supporter of the countless hosts, so 
much so that the amount of this gas found present in the 
air at any time and place is thought to be a fair indication 
of the relative number of organisms there present. More 
than two hundred distinct forms of microscopic animals 
have been discovered in the atmosphere* (Elirenburg). 
The precise effect of these organisms on health is not 
known, but it is generally believed the effect is detri- 
mental. Bacteria of many forms, and spores of fungi, 
are also found in the air, and all these organisms are 
known to thrive in the organic impurities found in the 
air. Painstaking investigations as to the disease-producing 
power of these organisms have been in progress within 
the past few years by Drs. Koch and Pasteur, and while 
it is generally believed that these organisms and certain 
diseases are related as cause and effect, no definite germ 
theory of disease has yet (1886) been accepted by the 
medical profession. The facts that are known, how- 

* The presence of organic matter in the air may be shown by the 
aeroscope, or by forcing air through strong sulphuric acid, when, if pres- 
ent, the organic matter will turn the acid dark. 



THE AIR. 27 

eyer, and in which we are here interested are : That a 
large number of impurities exist in the air — that these 
impurities congregate in inclosed, unventilated spaces 
where they are produced, and that they have a detriment- 
al influence on the health. 

The external air from which the school-room must be 
supplied has impurities peculiar to itself and to the lo- 
cality whence obtained. Dust and smoke exist in the air 
in large quantities, as well as the products of decaying or- 
ganic matter from the surface of the earth. Equal quan- 
tities of these impurities are not found in all parts of the 
air. Dust and smoke, owing to their tendency to settle, 
will be found in larger quantities nearest the earth. In 
a series of analyses on street-dust, at different ilevations, 
Tichborne found that the amount of dust was not only 
inversely proportional to the elevation, but that the per- 
centage of organic matter that it contained decreases with 
the elevation ; street-dust near the ground containing 45 '2 
per cent of organic matter, and that at the top of a pillar 
134 feet high only 29-7 per cent. The same must be true 
as to the relative quantity of organic impurities at different 
elevations. Gases rising from decaying matter on the 
earth must rise a certain distance before they can come 
into contact with sufficient pure air to dilute and diffuse 
them. The reason why 'Aground-air" is unwholesome 
is thus seen to be evident. The importance of these facts 
will appear when we come to consider the source of the 
fresh- air supply in ventilation. 

There are other sources of impurities, not to be over- 
looked, always existing in rooms heated by stoves or by 
the direct radiation of steam-pipes. The most serious of 
these is found in the use of stoves, which give off, when 
hot, a poisonous gas. The blue flame sometimes noticed 
in stoves, when coal is first put in, is due to the burning 



28 VENTILATION AND WARMING OF SCHOOL-BUILDINGS, 

of carbonic monoxide— 00 — a very poisonous gas. Iron, 
when moderately hot, is not pervious to this gas, which 
then passes harmlessly up the chimney ; but, when 
strongly heated, iron loses the power of retaining it, be- 
comes pervious, and allows the poisonous gas to escape 
into the room. 

Another source of impurity, which is common both 
to stoves and to steam-pipes, where the latter are exposed, 
is in the burning and charring of small particles of or- 
ganic matter which settle on them. This burning is 
known to have a very injurious effect on the breathing 
qualities of air in a room, and should be remembered 
when considering the choice of the method of heating. 

Humidity of the Air. — The quantity of watery vapor 
found in the air varies with the locality, temperature, 
and various local conditions, and is important from a 
sanitary point of view. The right proportion of moist- 
ure in the air constitutes one of the conditions of a 
healthy climate. In the heating and ventilating of build- 
ings, where the proper proportion of watery vapor is 
found not to be present, it may be supplied by artificial 
means. A knowledge, therefore, of the proper condi- 
tions of humidity, as well as a knowledge of the means of 
supplying them when absent, is thus seen to be impor- 
tant. 

In crowded school-rooms the symptoms of fainting 
often evinced by pupils is thought to be partly or wholly 
due to an insufficient amount of moisture in the air of 
the room. Other physiological symptoms of an atmos- 
phere too dry are parched lips and tongue, a dry, fever- 
ish condition of the skin, and, in those children predis- 
posed to lung diseases, a hacking cough, resulting from 
the desiccating effect of excessively dry air on the lungs 
and bronchial tubes. 



THE AIR. 29 

The drying power of air depends not so much upon 
the actual quantity of moisture already in the air, as 
upon the capacity of the air, under certain conditions, to 
receive more ; these conditions being mainly the varia- 
tions of temperature. If the air of a room containing a 
certain amount of moisture be raised in temperature sev- 
eral degrees, its capacity for more moisture may be much 
increased, while the actual amount already present may 
not be materially diminished. Hot air exj)ands, and is 
thereby rendered thirsty, greedily extracting water from • 
everything moist with which it comes in contact. Air at 
any temperature, when it contains as much vapor of water 
as it can hold without depositing it in the form of dew, 
fog, etc., is said to be saturated, but it is plains that air 
which is saturated at one temperature will cease to be so 
at a higher temperature unless more moisture be added. 
This point of saturation is called the dew-point. The 
dew-point — the temperature at which the vapor in the 
air condenses — is, therefore, variable, and always depend- 
ent on the amount of vapor of water in the air. The 
dew-point is taken as the standard in estimating the hu- 
midity of the air, and is taken as 100 per cent. 

The sanitary condition of the air, as influenced by 
humidity, has not received the attention that its im- 
portance demands, yet enough has been done to enable us 
to estimate within limits fairly narrow. Dr. de Chau- 
mont, in some experiments in various rooms containing 
air of standard respiratory purity, found that the average 
humidity is 73 per cent of saturation. This, it must be 
remembered, was taken in England, where the climate is 
much more moist than that of America. Probably an 
humidity somewhat less would answer for our climate, but 
in any case a given standard must be regarded as only 
provisional, changing with the temperature of the room 



30 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

at the time of testing ; 63° Fahr. was the temperature used 
in the experiments of de Ohaumont. 

Some observations have been made in this country by 
D. L. Huntington at the Barnes Hospital, Washington, 
and by Dr. Cowles at the Boston City Hospital. The 
results are as follows : "First week in December, 1877. 
Average external temperature 38^° ; average temperature 
of the wards, from 71° to 76° Fahr. Average relative 
humidity, from 44 to 49 per cent of saturation ; of outer 
air, 74." This, it will be noticed, shows a much lower 
per cent of moisture in the room than that given by the 
English standard, yet it was claimed that notwithstand- 
ing this small quantity "a peculiar feeling of freshness 
and purity was perceived by those who entered the room." 

This "peculiar feeling" which is always experienced 
in passing into a warm room in winter is, I think, hard- 
ly a trustworthy test of the atmospheric purity ; and it 
seems further unreasonable to suppose that the best sani- 
tary conditions would admit so great a difference as 74 
and 44 per cent between the outer and inner air. This 
opinion will be further strengthened if we accept the 
statement of Dr. Parkes, that "warmth and great hu- 
midity are borne on the whole more easily than cold and 
great humidity." There is little doubt that some differ- 
ence exists in the amount, of atmospheric moisture re- 
quired by different individuals, but arrangement should 
always be made to suit the average needs of the majority. 
From what I have been able to learn from study and ob- 
servation, I believe that 70 to 75 per cent may safely be 
taken as a provisional standard of humidity for the air 
of school-rooms. 

In rooms where the air is too dry, it may be moistened 
in winter by placing shallow vessels of water on stoves, 
on heating coils of steam or hot- water pipes, or in the 



EXAMINATION OF THE AIR. 31 

hot-air ducts. In summer, moistening by artificial means 
will seldom be required, but when, on account of unusual 
dryness of season, the conditions so require, it may be done 
by sprinkling floors (not a very advisable method), or by 
ejecting cold water in spray through a series of small holes. 
The humidity of the air may be determined directly 
by means of an hygrometer, or indirectly by means of wet 
and dry bulb thermometers. In most hygrometers a bright 
surface is cooled till dew is deposited thereon, and the 
temperature then noted. Owing to the sensitiveness of 
hair to changes in humidity, it is sometimes made use of 
as an hygrometer ; hair shortens in dry and lengthens in 
moist air ; and if a hair be fastened by one end to an in- 
flexible support and the other end attached to one eud 
of a needle hung on a pivot, the other end of the needle 
moving over a graduated scale, it will form a tolerably 
accurate measure of humidity. The method used by me 
is that of the wet and dry bulb thermometer with Glai- 
sher's factors. (See Appendix A.) 



CHAPTER IV. 

EXAMI^^ATIOK OF THE AIE. 

Microscopic. — The microscopic examination of bodies 
suspended in the air is rapidly growing in importance. 
While the work may still be regarded as in its infancy, 
much has been done by Koch, Pasteur, and others, to- 
ward determining the effect on the health of organic 
microscopic bodies in the air. 

It is, of course, not to be expected of one who is 
merely testing the respirability of the air in a school- 



32 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

room to searcli for specific disease-producing germs ; but as 
large quantities of dust, smoke, etc., suspended in the air, 
tend to make it irrespirable in proportion to the amount 
of these impurities existing therein, a knowledge of the 
relative quantity of suspended matter, as well as the nature 
of it, becomes a necessary part of the work of testing the 
fitness of air for respiration. A fair knowledge of the 
respirable quality can be obtained without microscopic 
tests ; but as these observations are otherwise interesting 
and instructive, I here describe the method used by me, 
which is only one of the many now in use by microscopists. 

Arrange a series of Woulfe's bottles containing pure 
distilled water, connected by tubes, and pass through this 
the air to be examined. The air in passing through the 
water leaves its suspended particles in the water, a drop 
of which can be examined under the microscope. If the 
water was pure distilled, all matter found in it in the 
experiment came from the air.* 

As a means of passing the air through the water, an 
air-pump or aspirator may be used. I use an air-pump 
which is so constructed as to admit the easy attachment 
of a small tube. The cubical capacity of the cylinder 
being known, the amount of air drawn through the water 
may be found by multiplying the capacity of the cylinder 
by the number of strokes. Should such a pump not be 
accessible, an aspirator may be made by taking a tin vessel 
of known capacity, with an opening at the top to receive 
the tube, and a tap below to let out the water. Fill this 
with water, attach the tube and open the tap ; as the 
water runs down, the vessel will be filled with air drawn 
through the water. 

* It is not, as some suppose, a native characteristic of water to con- 
tain " live things." Pure water is absolutely devoid of everything except 
its two constituent elements, oxygen and hydrogen. 



EXAMINATION OF THE AIR. 33 

The nature of the organisms in the air can be further 
studied, if desired, by passing the air through a cultivat- 
ing solution, which is set aside and the germs carefully 
studied from day to day as they deyelop. A solution of 
isinglass, two parts in 400 parts of pure distilled water 
(Fodor), makes a good medium. 

Chemical. — A complete analysis of impure air compre- 
hends the quantitatiye and qualitative tests for carbonic 
dioxide, COg, free ammonia, NH3, and other nitrogenous 
matter, oxidizable matters, nitrous and nitric acids, and 
hydrogen sulphide, HgS ; but for ordinary practical pur- 
poses the determination of the CO3 is by far the most 
important, and is ordinarily the only one which need be 
made. While the poisonous qualities of the ^ir are not 
wholly due to the presence of the QO^per se, the amount 
of this gas found to be present is, in air made impure by 
respiration, generally a good measure for other impurities 
to which the poisonous quality is principally due. Owing 
to this fact, a careful test for the amount of OOg contained 
in a given atmosphere is generally the only one which 
need be made where air is tested merely to determine ita 
respiratory purity. 

The mere presence of CO2 in the air may be tested by 
exposing baryta-water in a shallow open dish ; if OOo is 
present, a white deposit of barium carbonate will be formed 
on the surface of the liquid, the amount and rapidity of 
the formation being proportional to the amount of CO3 in 
the air. The exact proportion of CO3 in a given quantity 
of air may be determined by different processes ; but that 
of Pettenkofer, which is familiar to me by use, is probably 
as good as any. Briefly it is as follows : Take a glass bot- 
tle of about one gallon capacity — 4^ litres ; fill the bottle 
with water in the place where the air is to be tested. 
Pour out the water, allowing it to drain. This expels the 



34 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

air formerly in the bottle, and fills it with the air of the 
room. JSTow pour into the bottle 60 c. c. (cubic centime- 
tres) of clear lime- or baryta- water ; close the mouth odr- 
tight, and shake. Allow this to stand eight hours if lime- 
water, or one hour if baryta- water. The CO^ will all be 
absorbed by the water, the causticity of which will be 
lessened in proportion to the quantity of CO2 in the 
yessel ; the OOg, being acid, neutralizing the lime by 
forming a neutral carbonate. If now the causticity of 
the, water be known before and after the COg has been 
united with it, the difference will show the amount of 
lime which has united with COg. To find the causticity 
of lime, prepare an oxalic-acid solution.* Take 30 c. c. of 
fresh lime-water, like that used in the first part of the 
experiment, and mix with it just enough of the oxalic 
solution to exactly neutralize it.f The amount of the 
oxalic solution which will be required to do this will be 
somewhere between 34 and 41 milligrammes, the amount 
varying with the temperature. Now take 30 c. c. of the 
solution in the large bottle, after the expiration of the 
prescribed time, and try how much of the oxalic solution 
it takes exactly to neutralize it. The difference between 
this and the preceding shows tlie number of milligrammes 
of lime which were united with the CO2 contained in the 
air in the bottle. Multiply this difference by "795,1 

* This solution is prepared by dissolving 2*25 grammes of crystallized 
oxalic acid in one litre of pure distilled water ; 1 c. c, neutralizes 1 milli- 
gramme of lime, 

f It will be neutralized when it does not change the color of turmeric 
paper dipped into it. 

X The molecular weight of CaO (lime) is 56, and that of CO2, 44, the 
weight of CO2 being therefore ^'^ that of lime. The ratio between weight 
and volume at 32° Fahr. is -506. Then f|- x -506 x 2 = -im, the factor 
used above. The reason for multiplying by 2 will be evident by remember- 
ing that only 30 c. c. of the lime-water ^was used out of the 60 c. c. put in. 



EXAMINATION OF THE AIR. 35 

which gives the number of c. c. of CO2 contained in the 
air examined. Find the amount of air in the bottle by 
subtracting the volume of the lime-water put in, 60 c. c, 
from the total capacity of the bottle expressed in litres. 
The c.c. of CO2 divided by the volume of air will give the 
number of c. c. of OOg in 1,000 parts of air. The follow- 
ing general formula will be found useful in solving ex- 
amples : X — - ^—^ . Reference: a;=c. c. of COgper 

litre ; a = first alkalinity of lime-water ; a'= alkalinity 
after exposure to air in the jar ; c — capacity of the jar ; 
d = space occupied by the lime-water. When the air is 
several degrees either below or above the freezing point, as 
will generally be the case, a correction for temperature must 
be made, as a given volume of air when expanded by heat 
is less dense, and when contracted by cold more dense, 
than normal. " Air expands or contracts '2 per cent for 
every degree it deviates from the standard " ; hence '2 
per cent added to the result for every degree above 32° 
Fahr., or subtracted for every degree below 32° Fahr., 
will be a sufficient correction for temperature. At ordina- 
ry elevations a correction for pressure will not be necessary. 
The following example, selected from a series of ex- 
periments made by me, will be sufficient to illustrate the 
process. By first testing the alkalinity of the lime-water 
«=38 ; after exposure a'=30 ; c=4,500 c. c, d —-GO c. c. 

Then X = ^^^~^^^^J^^ =l-432 c.c. of COg per 1,000 vol- 
umes of air. Correcting for temperature, which was in 
this instance 80°, or 48° above 32°: 48 X •002+1x1-432= 
1-569. As there are only -4 c. c. CO2 in air of standard 
purity, the above test shows a bad condition of air. 

Prof. "William Jones proposes the following modifica- 
tion of this method, which will give the sanxe results, 
5 



36 VENTILATION AND WAEMING OF SCHOOL-BUILDINGS. 

lessening somewhat the work of calculation where a large 

number of tests are made. If we take the molecular 

weights of CO2 and H2C2O4 + 2H2O (oxalic acid), which 

are 43*89, and 125-7 respectively, we see that one part by 

125'7 
weight of OO2 is equal to ^^^, or 2*8639 by weight of 

II2O2O4 + 2H2O ; and as one part by weight of OOg is 
equal to 0*5086 part by volume, then each 2*8639 parts of 
oxalic acid are equal to 0*5086 part by volume of carbonic 
acid. Therefore 0*5086 : 28,639 : : 1 : 56,309, or 5 *6309 parts 
by tveight of oxalic acid are equal to 1 volume of carbonic 
acid ; consequently, if we dissolve 5*63 grains of crystal- 
lized oxalic acid in 1 litre of distilled water, 1 c. c. of this 
solution will be equal to 1 c. c. of COg, thus indicating the 
volume of CO2 present in a given amount of air by the 
difference in the number of cubic centimetres of oxalic acid 
solution required to neutralize a given amount of lime- or 
baryta-water before and after shaking with the air, with- 
out any more calculation ; except that if we use only one 
half the amount of lime-water that has been shaken with 
the air, it will be necessary to multiply the result by 2. 

In the absence of the means for chemical tests, the 
sense of smell by a healthy person may be employed with 
fair results. Dr. de Ohaumont states that *4132 parts of 
OO2 per 1,000 volumes of air can be barely perceived by 
the sense of smell carefully exercised. When 0*6708 of a 
part is present the organic matter becomes disagreeable, 
and when 0*9054 of a part is present it becomes offensive 
and oppressive. After this limit has been reached, and 
the air becomes loaded with still more impurities, the 
sense of smell becomes unable to, detect shades of differ- 
ence. He concludes, from a long series of such experi- 
ments, that ^^0*2 per 1,000 in round numbers is the maxi- 
raum of respiratory impurity admissible in a properly 



EXAMINATION OF THE AIR. 



37 



ventilated air-space." * It must be remembered that after 
the first few minutes in the room the sense of smell be- 
comes unreliable. This test can be applied only by per- 
sons of keen sense and close and discriminating judg- 
ment, and then only at the moment of first entrance into 
the room from pure external air. 



EXPERIMEI^TAL TESTS. 



No. of examination. . . . 


1 


2 


3 


4 


Time of day at which 










air was taken 


11a. m. 


2 p.m. 


11 A. M. 


4 p. M. 


No. of pupils in the 










room 


■ 50 


55 


45 


51 


No. and condition of 


8, all open 


6, three of 


8, three of 


4, on oppo- 


windows. 


above and 


them being 


them rais^ 


site sides 




below. 


op en 'at the 


from the 


and all 






bottom. 


bottom. 


open. 


External temperature. . 


50° 


75° 


60° 


70° 


Internal temp. ]^^°J^^ 


80° 
68° 


76° 

72° . 


88° 
76° 


70° 
68° 


Condition of the wind . 


Strong 


Calm. 


Gentle 


Gentle 




breeze. 




breeze. 


breeze. 


No. of parts of CO 2 in 










1,000 parts of air 










taken from near ceil- 










ino" 


3063 


3-387 


2-155 


1-055 


No. of parts of CO2 in 




1,000 parts of air 










taken from near the 










floor 


1-569 


1-923 


1-642 


•6415 


No. of parts of CO2 in 




1,000 parts of exter- 










nal air taken outside 










the building 


•bOI 


-513 


•493 


-486 


Method of heating. . . . 


Steam — 
direct ra- 
diation. 


No fire. 


Steam — 
direct ra- 
diation. 


No fire. 


Method of ventilating. 


One outlet, 


By windows 


One outlet, 






10x16 in., 


only. 


10x16 in.. 






into a shaft 




into a shaft 






without 




without 






heat. 




heat. 





* Roscoe found in a school of sixty-seven boys 3-1 parts of CO^ per 



38 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

The accompanying tabulated record shows the results 
of a few tests made by me on specimens of air taken from 
different school-rooms. 

These results show — first, that all the rooms from 
which air was taken contained an amount of COg consid- 
erably above the limit of respiratory impurity {i. e.,'A:-\- '% 
= '6 parts in 1,000 parts of air); secondly, that the amount 
of COg is due not so much to the number of hours the 
room had been occupied as to the conditions of yentila- 
tion. In Experiment 4, where the purest air was found, 
the room had been occupied all day, but on this particu- 
lar day the weather was fine, with a breeze from the west. 
The windows were on opposite sides, east and west, so 
that a current of air was passing directly through the 
room. On some other day, when the windows might have 
to be closed on account of bad weather, and the wind 
happened to blow in some other direction, this room 
would have no ventilating advantages over the others. 
Thirdly, that COg was in every case found in the largest 
quantities at the top of the room ; and, fourthly, that the 
external air is generally pure, so far as COg is concerned. 



CHAPTER V. 

AMOUl^T OF AIR EEQUIRED. 

When decided by examination that the air of a school- 
room is unfit for respiration, the question naturally pre- 
sents itself, How may this air be renewed, and what should 

1,000. "Weaver found in a girls' school in Leicester, England, 5*28 parts 
per 1,000. Pettenkofer found in an occupied room '7'23 parts per 1,000. 



AMOUNT OF AIR REQUIRED. 39 

be the rate of this renewal in order that it may be main- 
tained in a state of respirable purity ? Let us consider 
the latter question first : The amount of CO2 evolved by 
one person in one hour is — adult males, 0*7 of a cubic foot ; 
adult females, 0*6; children, 0*4. If we take 0*2 COg 
per 1,000 volumes of air as the extreme admissible limit 
of vitiation (and this is as much as is safely admissible), 
the number of cubic feet of fresh air which will be viti- 
ated by each person in one hour may be expressed by the 

formula v =^ -j, where v = the required amount of fresh 

air per hour ; a = the amount of CO3 exhaled by each 

person, and b = the limit of admissible impurity. In the 

case of children, where the amount of COg e:4^aled is 0*4, 

0-4 
we have by substitution j~^ = 2. 5 in the formula is ex- 

•^ 0-2 

pressed per thousand volumes ; therefore v represents the 
number of thousands of cubic feet of air. 

The number of cubic feet of air vitiated by each child 
in one hour is 2,000. In high-schools, where pupils are 
large, it would be more nearly coi^ct to use 0*6 of a 
cubic foot as the amount of COg evolved by each ; and in 
colleges 0*7 of a cubic foot, the amount given off by 
adults. These conditions, then, would require, respect- 
ively, for small children, 2,000 cubic feet per head ; for 
high-school pupils, 3,000 cubic feet ; and for college stu- 
dents, 3,500 cubic feet. In a school-room of ordinary 
size there are 28 X 34 X 14 = 13,328 cubic feet of air. 
From the foregoing it was seen that each child requires 
2,000 cubic feet of pure air per hour; sixty children— 
about the average school number — will therefore require 
the same amount in one minute. It is plain, then, to see 
that the air in the average school-room, were there no 
means for ventilation, would become vitiated in less than 



40 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

seyen minutes — 13,328 -i- 2,000 = 6-66+ mm. It ap- 
pears evident, then, that in order to meet the require- 
ments of perfect yentilation the air in the room must be 
changed every seven minutes, and the total amount of 
fresh air which must be passed through a school-room of 
ordinary capacity and occupancy is 2,000 X 60 = 120,000 
cubic feet per hour. 

After the first few minutes — the time required to viti- 
ate the amount of air the room contains — the size of the 
room makes no difference in the constant amount re- 
quired. It is the number and size of the occupants which 
must regulate the amount necessary for ventilation. The 
size of the room, and the number of cubic feet to be sup- 
plied each pupil, are important only for the fact that a 
given amount of air can be passed through a large room 
without producing strong currents more easily than the 
same amount through a small room. The size of the 
room, therefore, and the number of cubic feet per head, 
are no indications of the respiratory quality of the air 
therein contained. 

Hoio to Estimate the Amount of Air passing tlirougli 
a Room. — The air passing through a room may be esti- 
mated either by measuring it as it comes in or as it passes 
out. Before making these measurements they should be 
made intelligible by an understanding of a few funda- 
mental properties of fluids, of which air is one. 

All movement in the air is caused by an inequality of 
pressure in different' localities due to inequality of heat. 
Wind — air in motion — is simply the movement of the air 
of one locality toward another locality containing air of 
less density. As heat expands the air, making it lighter, 
the movement of the air will always be in the direction 
of the warmer temperature. The air, being matter, has 
weight, and is subject to the same laws of pressure and 



AMOUNT OF AIR REQUIRED. 41 

falling as other matter. If the atmosphere were of uni- 
form density from top to bottom, it would form an en- 
velope around the earth about five miles in depth. 

The velocity which a body acquires in falling is ex- 
pressed by the formula ?; = V2gE., where v = velocity, 
H = height through which the body falls, g = the accel- 
eration due to gravity. This is nearly equal to eight 
times the square root of^^the height, and for simplicity 
may be so expressed : S^v/H. 

The particles which constitute a fluid, as water or air, 
have no friction among themselves, and exert pressure in 
all directions. Another fundamental law following from 
this is that fluids will pass through an orifice below the 
surface with the same velocity that a body wguld acquire 
in falling a distance equal to that between the surface 
and the orifice ; and that, when passing through an orifice 
in a partition separating the fluid from another fluid of 
different height, the velocity will be equal to that of a 
body falling a distance equal to the difference of the 
depth of the fluids on the two sides. The pressure of the 
air on any surface near the earth is about fifteen pounds 
to the square inch, and is the weight of a column of air 
five miles in height. Air, then, would rush into a vacuum 
with a velocity which a body woald acquire in falling five 
miles. It would rush into a room containing air of a less 
pressure, which may be considered as a partial vacuum, 
with a velocity due to a height which represents the dif- 
ference between outside and inside pressure. Now, a di- 
rect relation exists in any substance between weight and 
density, and as a volume of air increases regularly with 
the temperature, lessening its density and weight in the 
same ratio, a means for measuring the difference of press- 
ure by comparing the temperature of the air on either 
side of the partition is thus afforded ; and this, together 



42 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

with a comparison of the relative height of the entrance 
and exit orifices in a room, enables ns to calculate the 
Telocity with which air is passing. 

Air expands -^j of its volume for every degree Fahr- 
enheit. The height through which a body would fall 
having the required velocity which we are considering 

h X t 
is expressed by the formula H = , where H = the 

height through which a body would fall to acquire the 
velocity under consideration ; h = height from the en- 
trance to the exit orifice ; t = the difference in tempera- 
ture between inside and outside. By substituting this 
value of H in the general formula {v = 8 ^H) for falling 

bodies, we have v = 81/ -77-7- in feet per second. 

' 491 ^ 

Example : Suppose h = 14 ft., ^ = 20°; then v = 

/14 X 20 
— J—. — = 6*032 + ft., the velocity of the air per sec- 
ond. An allowance of from one sixth to one half of the 
theoretical velocity must always be made for friction,* 
according to circumstances and special peculiarities of the 
openings and ducts or tubes leading thereto. Having 
found the velocity, the amount of fresh air may be found 
by multiplying the velocity by the sum of the areas of 
the openings expressed in feet. 

These calculations are equally true whether the open- 
ings are windows or apertures constructed especially for 
ventilation. When windows are used, a difficulty arises 
in making the computation, due to the difficulty of ascer- 
taining where the air enters and where it leaves the room; 
windows on different sides of the room, being of the same 

* Por discussion of particular cases and practical formulas for deter- 
mining velocity, see Appendix " B." 



AMOUNT OP AIR REQUIRED. 43 

distance from the floor, and their openings at different 
times varying in position and size to suit the freaks of 
the occupants, are inlets or outlets according to the cir- 
cumstances. The same window may be inlet and outlet 
at the same time, producing cross-currents and strong 
draughts, the disagreeable nature of which is well known 
to all victims of window-ventilation. 

The simple conditions governing the possibilities of 
this method of measuring the amount of air which is 
passing through a room are, that the air in the room 
must be of a higher temperature than that outside ; the 
air must pass in from below and pass out above. In sum- 
mer, when the outside temperature is equal to or higher 
than that inside, this method is not available. It is also 
unreliable when the wind is blowing, unless tire openings 
are properly guarded against the unequal pressure due to 
this cause.* 

The A7iemometer. — When the wind is blowing, or any 
of the conditions of the above method of measuring the 
velocity of the air are otherwise not complied with, the 
anemometer must be used. Of these instruments many 
kinds are now in use, but in principle they are all essen- 
tially the same. They consist of fans revolving on an 
axis (after the manner of a wind-mill) which is connected 
by wheel- work with an indicator showing the velocity of 
the air which is moving the fans. 

Insufficiency of ordinary Air- Supply. — School-houses 
which make pretensions to ventilation other than by 
means of doors and windows commonly have a single 
register for the admission of fresh air, and one for the 
exit of foul air. These are variously situated — some- 
times at the top of the room, sometimes at the bottom, 

* See " Regulating the Drafts of Openings," page 56. 



44: VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

and at other times midway between floor and ceiling. 
The proper position for these yentilating openings will be 
considered in another place ; bat^ supposing them to be 
situated properly, we are ready from the foregoing to con- 
sider the efficiency of these breathing-holes. 

These registers are usually about 16 X 18 inches, and 
sometimes much smaller; this gives a total area for the 
entrance of pure air of 288 square inches, or 2 square feet; 
multiplying by 6, the number expressing the velocity in 
the example previously given (where the height of the 
room is 14 feet, the difference between the temperature 
of air outside and inside 20°), we have 12, the number of 
cubic feet of air passing into the room per second ; mul- 
tiplying this by 3,600, we have 43,200, the number of 
cubic feet of air passing into the room per hour. We saw 
above that each pupil requires 2,000 cubic feet per hour 
in order that the degree of vitiation may not exceed the 
limit, 0'2 of a part of CO2 per 1,000 parts of air ; and that 
sixty pupils require 120,000 cubic feet of pure air per 
hour. It thus becomes evident that this amount of open- 
ing will ordinarily supply only about one third of the 
quantity of air required. Air passed through an opening 
of this size, in order to be sufficient, would have to move 
at the rate of about eighteen feet per second, or about 
eight and a half miles per hour. When air is moving 
two miles per hour, it becomes perceptible to the senses as 
wind ; and if it were passing into a room at the rate of 
eight miles an hour it would be a breeze which would be 
dangerous to the pupils sitting near it, especially if it was 
not warmed before passing in. This velocity of air would 
be neither tolerable nor possible, unless it should be first 
warmed and then forced into the room by means of aspi- 
rating chimneys, or by mechanical means described in 
another place. 



GENERAL PRINCIPLES OF VENTILATION. 45 

Tlie Distribution of Air, — No less important than the 
adequate quantity of air to be supplied to a room is its 
proper distribution. This is impossible where but a sin- 
gle opening is furnished for admission, and the same for 
exit. Under these conditions the air may pass through 
the room in a narrow current, without being utilized by 
mixing with the vitiated air of the room. 

In considering these single openings of the ordinary 
size, I have supposed the conditions such as to make them 
count for their greatest possible utility ; but when we 
remember that they are often misplaced — that the differ- 
ence in internal and external temperature is often not so 
favorable as the case considered; that the passages through 
which the air must pass before reaching the room, and in 
making its final escape in leaving it, do by fricEon greatly 
lessen the amount given by the theoretical estimate; and 
that these passages are often neglected and impure — we 
are forced to the conclusion that this much provision for 
furnishing pure air to a school-room is in its effects, if not 
absolutely nil, so very little that it may be ignored. The 
further conclusion is, that what air pupils generally get 
comes in through windows and doors. 



CHAPTER VI. 

GEISTERAL PRIKCIPLES OF VEi^TILATIOl!^. 

Hayin'G learned something of the nature and require- 
ments of the air we breathe, of the source of its impuri- 
ties, the amount needed, and the way by which it may be 
measured, we are ready to consider how a room is to be 
supplied with air of the requisite quantity and quality. 



46 VENTILATIOX AND WARMING OP SCHOOL-BUILDINGS. 

and how its proper temperature may be maintained. How 
to remove the air from a room as fast as it becomes viti- 
ated, and to supply its place with pure air of the proper 
temperature, are questions in engineeriag, to answer which 
is at once necessary and difficult. 

The difficulties which attend the answering of these 
questions are in part theoretical and in part mechanical ; 
theoretical, in that all devices and means to accomplish 
the ends of ventilation must rest on general principles, 
and conform to the known laws of matter and motion ; 
mechanical, in that the successful application of the most 
obvious general principle implies good workmanship. 

The most perfect theory of ventilation, based on cor- 
rect physical principles, might be totally defeated in its 
ends by a bungling carpenter. These important ques- 
tions, then, can be met and answered only by accurate 
and skillful workmanship, based on correct theory. 

A secondary difficulty attending all efforts to engineer 
air is that it is invisible. Could the air and the impuri- 
ties which it contains be seen, we should at every turn 
receive practical hints how to move it, as well as constant 
admonition that it is to our best interests to do so ; but, 
instead of the advantages which the visibility of the air 
would afford, we have to rely on our knowledge of its 
properties and laws, and on our reason in interpreting ex- 
isting causes and their attendant effects. 

Warming and ventilating are antagonistic processes — 
the one is addition, the other subtraction ; the one a giv- 
ing, the other a taking away. But, as the two processes 
are inseparably connected and mutually interdependent, 
it will be necessary, partially at least, to treat of them 
together. 

Natural and Artificial Ventilation. — So many differ- 
ent devices of warming and ventilating have been em- 



GENERAL PRINCIPLES OF VENTILATION. 47 

ployed, some of which make use of mechanical means 
to move the air, that ventilation is usually considered 
under two classes — natural and artificial ventilation. 

In natural ventilation the openings are so constructed 
and arranged as to make the natural forces in the rising 
of warm air, and in the falling of cold air, do the work of 
changing the air of the room. 

In artificial ventilation, the air is forced into the room 
by mechanical power. 

This classification, while convenient enough, is, after 
all, entirely arbitrary. All ventilation is in one sense 
artificial, and in another sense all ventilation is natural. 
*^ Natural" ventilation is artificial, as it requires art in 
making the openings of the proper construction and po- 
sition ; "artificial" ventilation is natural in^hat natural 
laws must be utilized and directed. 

Illustration of the General Tlieory of Ventilation. — 
As the laws of motion and pressure governing fluids are 
equally applicable to air and to water, the following in- 
teresting experiment illustrates the general theory of 
ventilation : 

Take a large glass jar and fill it with clear water to 
represent the external atmosphere. Fill a large square 
bottle, having apertures near the top and bottom, with 
colored water to represent the internal air of the room 
and its impurities ; see that it is of the same temperature 
as the water in the jar, and then suspend the bottle in 
the water in the jar. On carefully opening the apertures 
it will be noticed that a mingling of the clear and colored 
waters takes place very slowly. This is due to diffusion, 
and illustrates what takes place in the air when the in- 
ternal and external temperatures are equal and the at- 
mosphere quiet. If now the colored water be heated to a 
temperature several degrees above that of the clear water, 



48 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

it will be seen to rise and pass out of the upper apertures, 
the outside clear water, being heavier, flowing in at the 
lower aperture. The colored water soon passes out, leav- 
ing the bottle filled with the pure water. This illustrates 
ventilation in winter, when the air of the room is warmer 
than that outside. If the colored water in the bottle be 
cooled by ice or a freezing mixture, and the outside water 
be warmed, the current will be reversed ; the heavier, 
cool colored water will flow out at the lower aperture, 
and the outside clear water will flow in through the upper 
one to fill the space thus left. This illustrates the action 
of the air in summer, when the air of the room is cooler 
than the air outside. 



CHAPTER VII. 

NATUKAL VENTILATION. 

Position of Ventilators. — The question is often asked. 
Where should ventilators be placed ? Some say at the 
top of the room, others say at the bottom ; the experi- 
ment described in the foregoing chapter answers this 
question. When only the conditions of ordinary natural 
ventilation are present, there can be but one answer — 
ventilators should he at the top of the room. The air in 
the room, when warmer than the outside air, must come 
in at the bottom and go out at the top ; and, when cooler 
than the outside air, must come in at the top and pass 
out at the bottom. 

This movement may be reversed, but it must be done 
by means other than that afforded by natural ventilation; 
and, even in the plenum movement described in another 



NATURAL VENTILATION. 49 

place, it is always the part of economy to work with Na- 
ture, and not against her. 

Ventilators are often placed near the floor because of 
the erroneous idea that the foul air is below. The fact 
that CO2 is a little heavier than air has led to the hasty 
conclusion that it at once settles, and is to be found near 
the floor. The facts are that COg forms a very small per- 
centage of each expired breath, and its temperature, as well 
as that of the air from the lungs with which it is mixed, is 
when leaving the mouth much higher than that of the sur- 
rounding air ; it is therefore lighter, and at once rises ; and 
the tendency it has toward rapid diffusion prevents its sink- 
ing even after it has become as cool as the air of the room. 

The tendency which gases of great diffei^nces of den- 
sity have to diffuse, even against the force of gravity, may 
be illustrated by taking two bottles, filled, one with hy- 
drogen, the lightest gas known, and the other with the 
heavy OO2 gas which we are considering. Connect the 
bottles by a glass tube passing through the cork stoppers 
of each. Leave them for a time with the light hydrogen 
above and the heavy COg below, and in a short time they 
will be thoroughly mixed, the heavy gas having risen 
against gravity to mix with the hydrogen. 

In certain modern systems of heating and ventilating, 
to be described hereafter, the ventilating ducts are placed 
near the floor. This is thought by the inventors of these 
systems necessary to prevent the too rapid escape of the 
fresh air as it enters the room and immediately rises to 
the top. If this warm air were properly distributed as it 
entered, it would be sufficiently vitiated to require its 
removal on reaching the top of the room ; but, as this is 
seldom the case, the difficulty is met by placing the out- 
lets below, allowing the upper hot air to press the cooler 

air down and out. 
3 



50 VENTILATION AND WARMING OF SCHOOL-BUILDINGS, 

As a justification for this arrangement, the authors of 
these systems have tried to persuade themselves and the 
public that the foul air of a room is at the bottom, and 
have conducted some curious experiments to prove this ; 
among which may be mentioned those of Mr. Leeds, of 
Philadelphia. 

He first takes a large glass tube, with perforated caps 
at each end, as represented in Fig. 1. Smoke is blown 

Fig. 1. 



-''-■ — *;r" — -~-'^^^^*» 



into the tube through the rubber tube T. It will first 
rise to the top of the tube, but on cooling it soon settles 
to the bottom and flows out at A. This smoke is intended 
to represent the carbonic- acid gas, CO2, from the lungs, 
which it is claimed by this experiment will fall like the 
smoke at a temperature of from 60° to 70°. 

This, with no further knowledge of the nature of 
smoke and 00^, would readily pass for a legitimate com- 
parison ; but a moment's reflection reveals a fallacy. 
Smoke is solid matter in a fine state of division floating 
in warm rising air. When the air cools and ceases to 
rise, these solid particles by their superior specific gravity 
fall. But CO2 18 not a solid; it is a gas ; and gases have 
the property of rapid diffusion. The relatively small 
quantity of CO3 at any one time rising with the heated 
air will have more than time thoroughly to diffuse in the 
air before the latter cools sufficiently to allow the settling 
of a similarly suspended solid. 

Another alleged proof, by the same author, consists 



INLETS. 51 

of admitting some COg in an undiluted state into an in- 
closed space in which tapers are burning at different 
heights. The COg being heavier than air, when thus 
poured in, of course sinks to the bottom, and extinguishes 
the lower lights first, which is given as sufficient proof 
that foul air is found at the bottom of the room. Here 
the quantity of CO3 used, and the time given for its dif- 
fusion, are all out of proportion with the actual con- 
ditions ever existing in an occupied room. 

Experimental demonstration does not always demon- 
strate. Nothing may be more misleading in its teaching 
than an experiment which is only half interpreted. Should 
this reasoning be thought insufficient, the facts may be 
easily ascertained by examining the air fo|^ COg. (See 
Experimental Tests, page 37.) 



CHAPTER VIII. 

♦ IKLETS. 

Position. — Inlets, as before intimated, should be placed 
near the floor. It is sometimes claimed that in order to 
avoid cold air on the feet the inlets should be placed seven 
to nine feet from the floor, so that the cold air on entering 
may sink and mingle with the warmer air of the room as 
it descends. Too much can not be said against submitting 
the occupants of a room to cold drafts of air ; and where 
the air is allowed to enter without being warmed, or with- 
out provision being made for its warming as it enters, it 
is perhaps less objectionable to admit the air from above ; 
but, as it should be a settled principle in building school- 
houses that the air should never enter without some pro- 



52 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

vision for its warming, the objection to its admission 
from below disappears. To admit it from anywhere else 
is practically to destroy the npward direction of the cur- 
rent, upon which the regular change of the air of the room 
mainly depends. 

In summer, when the inside air is sometimes cooler 
than the outside, the ventilation will be downward, and 
the inlet and outlet openings at the bottom and top of 
the rooms respectively will change functions, the air com- 
ing in at the top and going out at the bottom ; but this 
is not often the case, especially in school-houses where 
school is not in session during the hottest weather. 

Total Size and Distribution of Inlets. — Inlets should, 
of course, be of sufficient area to admit the requisite 
amount of air without requiring so high a velocity as to 
cause drafts. The total area may be easily approximated 

V 

by the formula A — -———-,, Avhere A equals the sectional 

•^ 0,K)\J\}V 

area of the inlet ; V equals the volume of air passing 
through the inlet per hour ; v' equals the velocity of air 
in feet per second through the inlet ; 3,600 equals num- 
ber of seconds per hour. It is generally more convenient 
to let A represent the number of cubic feet of air required 
per hour by each pupil, then the amount required for 
any number of pupils can easily be obtained. The value 
of V has already been discussed. (See Appendix "B.") 
Example : 

What will be the total sectional area of inlets required 
in a room capable of accommodating 75 pupils ? If each 
pupil requires 3,000 cubic feet per hour, and the velocity 
with which the air can be admitted is found to be 7 feet 

per second, then A = ^ '^ — - = '119 square foot = 17*1 

^ ' 3,600x7 ^ 

square inches for each pupil. By referring to the exam- 



INLETS. 53 

pie in Appendix *^B/' it will be seen that 7*7 is the ve- 
locity attained when a good aspirating chimney is used. 
It often hajDpens in ordinary conditions of natural venti- 
lation that the velocity is not more than 5 feet per second. 

Using this number in the aibove problem, A = ^ — - = 

OjOUU /\ o 
-| square foot, or 24 square inches. Counting 60 as the 
number of pupils to be supplied, the total area of inlets 
will be 60 X 24 = 1,440 square inches. This is equal to 
one inlet 37*8 inches square, or 10 square feet. About 
the same area is required for outlets, making 20 square 
feet as the total area required for inlets and outlets in an 
ordinary school-room. 

Distribution of Inlets. — The air should n^ver be ad- 
mitted through a single inlet, but should be so distributed 
around the room that free diffusion may occur. To pass 
air into a single opening of a large room, and allow it to 
pass directly out at another opening, may be likened to a 
waiter who would feed a company by carrying a quantity 
of food through a dining-room without stopping to pass 
it around. One foot square is large enough for one 
opening. In the example given above we have then ten 
openings, which should be equally distributed around the 
room ; the same number of outlets would not be re- 
quired, though they must be equal in area. 

Source of the Air supplying Inlets. — It is an im- 
portant matter, though often overlooked, that the air 
which furnishes the supply to inlets should come from 
a pure source. It is generally understood that the sur- 
face condition of any locality determines largely the 
condition of the air which comes in contact with that 
surface. A wind, if blowing over an icy region, will be 
cold ; if across a dry and arid region, it will be dry, des- 
iccating, and parching ; if over a swamj^y, wet locality. 



54 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

where large quantities of organic matter are in a state of 
decay, it will be laden with sickening yapors and mala- 
rial germs. 

In full knowledge of these universally recognized facts, 
the air which furnishes the inlets is often drawn from 
near the damp ground, and sometimes from the vicinity 
of back yards and alleys, where all kinds of filth and ref- 
use pollute this ^^ fresh supply" before it enters the 
school-room. 

Unless the school-house is extremely fortunate in its 
location-site, and at some distance away from all other 
buildings, the air supply should be drawn at some dis- 
tance from the ground, by means of upright shafts or 
tubes of the height determined by the circumstances of 
each case. Fig. 2 illustrates the movement of the air 
down the shaft, through the room, and out at the venti- 
lator. A, downcast tube, with conical-shaped cap in- 
verted ; B, entrance shaft ; 0, upcast cowl, with conical- 
shaped cap erect ; D, outlets in the ceiling ; E, registers 
admitting air into the room ; E, room ; W, windows. 

The chief objection to the use of down shafts for the 
purpose of getting pure air is to be found in the retarda- 
tion due to the friction. This may be entirely overcome 
by means of aspirating chimneys, but even when these 
are absent the friction may be largely compensated for by 
properly arranging the shape of the shafts and Tentila- 
tors. Eeference to Fig. 2 will show how this may be done: 
the wind striking the inclined surface of the inverted 
conical cap is deflected downward into the shaft, thus 
increasing the amount of air entering the room. In the 
ventilator 0, on the other hand, the wind striking against 
the oppositely inclined surface of the erect conical cap, as 
well as the flange C below, is deflected upward, causing 
an upward draft in the ventilating tube. 



INLETS. 



55 



"Lobster-backed" cowls are sometimes used on venti- 
lators to increase their aspirating power. These revolve 



Fig. 2. 



B 



w 




R 




w 







i 



with the wind, keeping the back to the windward, thus 
preventing the wind from blowing down the tube ; the 



56 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

liability, however, of these cowls to get out of order lias 
led to their disuse. 

All shafts and tubes leading to the room should be so 
constructed as to reduce friction to a minimum, and ad- 
mit of frequent cleaning ; they should therefore be lined 
with some smooth, hard material, and be made accessible 
to the brush of the janitor. Neglect in this particular is 
often a considerable source of vitiation. Eough brick and 
mortar shafts and ducts collect large quantities of dirt 
and organic matter, which by its decay forms a source of 
pollution, and, being by their construction inaccessible, 
their vitiating action is constant. 



CHAPTER IX. 

EEGULATIKG THE DRAFT OF OPENINGS — THE WIND. 

We have discussed in another place the nature and 
velocity of air passing through inlets and outlets, when 
caused by the inequality of internal and external temper- 
ature, and the difference in height between inlets and 
outlets. But the results thus obtained will nearly always 
be modified by the action of the wind, which is usually 
blowing in some degree, and which must be in some man- 
ner compensated for by properly arranged inlets. 

The action of the wind is to increase the pressure of 
the air on the windward side of the room, and by the aspi- 
rating power which a moving air-current has on neigh- 
boring air to decrease the normal j^ressure on the leeward 
side. The extra pressure exerted by the wind may be 
estimated by first ascertaining the velocity by means of an 
anemometer {q, v.), squaring and multiplying by '005. 



REGULATING THE DRAFT OF OPENINGS. 57 

This is expressed by the empirical formula v^X "005 = P, 
where v = velocity of the wind, P = pressure in pounds 
per square foot, and '005 = a constant. 

When an anemometer is not accessible, a tolerably 
correct estimate of the wind's pressure may be obtained 
by Beaufort's classification of winds : 1, faint air; 2, light 
air ; 3, light breeze ; 4, gentle breeze ; 5, fresh breeze ; 6, 
gentle gale; 7, moderate gale; 8, brisk gale; 9, fresh gale; 
10, strong gale; 11, hard gale; 12, storm. In this classi- 
fication the force of the wind is estimated by the scale 
to 12, which represents all degrees from a calm to a hur- 
ricane. In using this, any estimate divided by 2, and 
the result squared, will approximately represent the wind's 
pressure in pounds. Example: Suppose a " gentle breeze " 
is blowing. Eeferring to the classification aoove, it is 
seen that *' gentle breeze " is No. 4 ; then (f )^ = 4, the 
number of pounds pressure on one square foot of surface. 
Again: If a ^^ strong gale "is blowing, then (J^)' = 25 
pounds. 

In the absence of an anemometer, the velocities of the 
different winds above enumerated may be calculated by 
finding the pressure in each by the method last given, 
and then substitute this value of P in the first formula, 
from which then find the value of v. For convenient 
reference I have made the calculations, which may be 
considered as simply a popular translation into the com- 
mon lan^ruasre of terms used in referring to wind : 



1. 


Faint air, 


7 miles per hour. 


2. 


Light air. 


14 '•' 


3. 


Light breeze. 


21 '' '' 


4. 


Gentle breeze. 


28 " '' 


5. 


Fresh breeze, 


35 '' '' 


6. 


Gentle gale. 


42 '' " 



7. Moderate gale, 49 



58 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 



8. 


Brisk gale, 


56 


miles per hour. 


9. 


Fresh gale. 


63 


a a 


10. 


Strong gale, 


70 


a a 


11. 


Hard gale. 


78 


a a 


12. 


Storm, 


85 


a a 



If action of the wind is not anticipated and provided 
for, it will defeat the most carefully laid plans for venti- 
lation ; but, if properly controlled, it may by its perflat- 
ing, aspirating, and motive power be made an aid instead 
of being a hindrance. By its perflating power it may be 
used in counteracting friction by directing the current 
downward through entrance shafts, as shown in Fig, 2 A. 
By its aspirating power it may increase the upward draft 
of a ventilator chimney by blowing directly across the 
top, or by being directed upward by means of a deflecting 
surface (Fig. 2 0). 

When inlets are not preceded by down -shafts, but only 
by short tubes or ducts coming directly from the outer 
air, they should be guarded by means of guards or yalves, 
to prevent strong gusts of wind from entering the room, 
which might otherwise occur. The best possible arrange- 
ment for this purpose would be a modified form of Dr. 
Arnott's current-regulating air- valve, which he invented 
for regulating the draft of closed stoves. A sectional 




Fig. 3. ^ 



"c^,-^^ 



1 



.A 






diagram of this ingenious device is here represented (Fig. 
3). The bounding lines H E I K represent the outside 



REGULATING THE DRAFT OF OPENINGS. 59 

walls of tlie tube to be fitted into the inlet duct. The 
arrows show the direction of the air-current ; A I is the 
opening of the inner extremity of the box, and D H the 
opening to the outer extremity. G E represents the edge 
of a lever-frame balanced across the partition C B. F G 
is a door attached to the lower extremity of the lever- 
frame EG. W is a sliding weight on the rod extending 
from F. The half of the lever-frame shown by the broken 
line C E is covered by a wire screen, through which the 
air-current flows in its passage into the room. If the 
current is strong, it is resisted somewhat by the friction 
against the wires. This resistance causes the screen end of 
the frame to be depressed, and the o])posite end, carrying 
the door F, to be elevated — thus partly closing aperture 
H D. The size of the opening will thus always be in- 
versely proportional to the strength of the wind. When 
out of proper balance, it may be corrected by moving the 
weight W. This device is remarkable for its ingenious 
simplicity, and it is also remarkable that it has never 
been utilized as a current-regulator in ventilation. 

Various devices have been contrived at the inner ter- 
minus of inlets for preventing a perceptible draft on the 
windward side of buildings, among which may be men- 
tioned the Shirringham valve, which gives the wind a de- 
flection upward as it enters the room. Other forms have 
been made by Messrs. Bayle, Weaver, and Ellison. All 
these, however, must be regarded as so many attempts to 
correct what ought not to exist. If the velocity of wind 
is not checked before it reaches the inside of the room, it 
is then too late to manage it satisfactorily. The wind 
might be successfully managed, and the air at the same 
time be freed from many of its suspended impurities, by 
constructing, outside the building to be supplied, large air 
receptacles supplying the inlets. These receptacles would 



60 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

serye a purpose in supplying air analogous to that of our 
large reservoirs in supplying water. The entrance to 
these receptacles could be guarded by filters for abstract- 
ing suspended impurities; andihe fluctuating air pressure 
due to the wind could be regulated by automatic valves. 

Admitting Air at the Top. — When a room is situated 
so as to make the admission of the air at the bottom in- 
convenient, it may be admitted from the top. Fig. 4 
represents McKinnell's circular tube, which is probably 
the best arrangement for this form of ventilation. The 
heat of the room causes the air to rise and pass out at the 
inner tube, as indicated by the arrows. The addition of 
the cowl A would tend to promote the same upward cur- 
rent. The partial vacuum thus formed will be filled by 
the outside air flowing in at the large encircling tube, the 
action of which would be further promoted by the addi- 
tion of the inverted flange B. The horizontal flange 0, 
at the lower extremity of the inner tube, deflects the in- 
flowing air along the ceiling, distributing it before it falls 
to mingle with the warm air of the room. 

This method of admitting the air has some advantages. 
The cold air, by its contact with the warm air near the 
ceiling, becomes warm before reaching the occupants of 
the room. By its admission through a tube encircling 
the warm inner tube, the inflowing air, if cold, becomes 
warm by contact. This tube will not always act as an 
outlet. If the windows are opened, cold air will come in 
from below, supplying the place of the ascending warm 
air, which will then pass out at both tubes, making them 
both outlets. 

The conditions of natural ventilation may be sum- 
marized briefly : The air of the room, made warm by 
artificial means, and by the heat of bodies, has a tendency 
to rise ; that it may pass put as fast as vitiated, this ten- 



REGULATING THE DRAFT OF OPENINGS. 
Fig. 4. 



Gl 




dency must not be resisted, but promoted by openings 
from above into aspirating cowls or chimneys. Fresh air, 
which supplies the place of the outgoing air, must be so 
admitted as to facilitate the same movement by utilizing 



62 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

its power to push. In order that it may be pure, it must 
be taken from an elevated source by means of an upright 
shaft. The regularity of the supply must be regulated 
by properly constructed valves. 



CHAPTER X. 

VENTILATION BY WINDOWS. 

The primary office of windows is to admit light ; but 
owing to a lack of proper provision for the passage of 
fresh air, they must also serve the secondary office of 
ventilation. It has already been shown that, where ven- 
tilators exist, they are usually only nominal, their size, 
position, and construction making their utility almost 
wholly imaginary. As windows, then, in school-houses 
already existing, are our only source of fresh air, and 
furnish us the only means that we may soon reasonably 
hope for, it behooves us to make the most of them. 
Where the means are meager, their skillful manipulation 
becomes still more a necessity. Generally speaking, win- 
dows are poor ventilators. On a balmy day in spring, 
when the sky is clear, the dust having been laid by a 
light shower, and a gentle zej)hyr is blowing, all the 
windows may be raised (or dispensed with entirely), and 
the air allowed to circulate freely through the room. 
Under such circumstances, windows are the best pos- 
sible Tentilators, unless it were possible to remove the 
walls also. To ventilate a room on such a day re- 
quires little forethought. The common instinct of a 
school-girl to throw open a window is all the art or phi- 
losophy which the case requires. But when the bitter 



VENTILATION BY WINDOWS. 63 

winds of winter are blowing, or rain or snow is pelting 
one side of the house, or perhaps clouds of dust and 
smoke are rolling toward the house, the case is different ; 
the instinct which throws up a window to escape a stifling 
atmosphere, throws it down again to escape a worse evil. 

When wind has any of the disagreeable accompani- 
ments above mentioned, the windows should, when possi- 
ble, be opened on the leeward side. The aspirating power 
of the wind has a vacuum-forming tendency on the side 
opposite its direction ; the air will, therefore, if windows 
be opened on that side, flow out of the room, and suffi- 
cient air to supply the vacancy thus made will work its 
way through cracks and crevices on the windward side. 

It often occurs that windows are all on one or two 
sides of the room ; we then have our choice oetween the 
suffocation of closed windows or braving the elements 
admitted by open ones. Where the only windows happen 
to be on the windward side, and the wind must be ad- 
mitted, it is better to open them at the top. The wind 
will blow in, forcing some of the impure air out. 

Just where the outlets will be can hardly be guessed. 
About half of the openings to a room, when there is move- 
ment of the air through them, must of necessity be out- 
lets. Where the outlets are will depend upon the posi- 
tion of the inlets and the freaks of the wind. A single 
opening will sometimes be both inlet and outlet where 
shifting cross-currents are irregularly passing. The air 
which thus enters will in some measure mix with the 
vitiated air of the room, diluting the exhaled poisons. 
The air which is forced out will carry with it some of the 
impurities ; the amount, however, depending on local and 
changing conditions. This kind of ventilation may be 
likened to the imperfect blood-circulation in the cold- 
blooded reptiles, which have a single ventricle for both 



64 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 



pure and impure blood, which is sent through the system 
in a mixed state. 

The force of the wind admitted through open single 
windows may be partially checked by fastening a piece 
of board to the top sash and extending into the room ob- 
liquely upward so as to retard its fall on the heads of the 
pupils. In Fig. 6, a, the arrows show the direction of 

Fig. 5. 




m 



W 



R 



-h 



m. 



>^^^^:m^^^-^^j^^m^^.^^^^j^^ 



the air deflected upward as it passes into the room, E, by 
the oblique board, «, attached to the upper sash ; 5, on the 
other side, represents a board fitted between the casings on 
the window-stool, and serves a similar function. 

Ko set rules can be given as to whether windows should 
be opened from the top or from the bottom. This will 
depend entirely upon the circumstances — ^upon whether a 
window when opened is intended for an outlet or an in- 
let. This requires close observation on the part of the 



VENTILATION BY WINDOWS. 



65 



teacher, as well as careful study and an intelligent under- 
standing of the existing conditions. When the wind is 
not blowing, all the windows should be opened, both top 
and bottom ; the size of the openings being regulated to 
suit the temperature. In this way the air of the room, if 
it is warmer than the outside air, will rise and pass out at 
the top ; the outside air, being heayier, will flow in at the 
bottom. In summer, when the air of the room is cooler 
than that on the outside, the current will be reversed. 

When the internal and external temperature is about 
equal, and when no wind is stirring, the windows should 
be opened about equally from above and below, and as 
wide as possible, giving diffusion, the only means for ven- 
tilation which is under the supposed condition's existing, 
as much freedom as possible. 

It is when the wind is blowing that the greatest diffi- 
culty is found in ventilating by windows, but by skillful 



Fig. 6. 




.<C\\\v\\^\vv\vvv^\\vv^v^^^^ 



management much more can be done toward establishing 
a constant current than is generally supposed. The most 
favorable condition is when windows are on opposite sides 
of the room. Fig. 6 supposes this case, where a moder- 



QQ VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

ate wind is blowing from the direction indicated by the 
large arrows. By opening the window on the windward 
side at the top, and the one on the leeward side at the 
bottom, a current is established as indicated by the large 
inside arrows ; this direction being the resultant of two 
forces — one the horizontal force of the wind, the other 
the greater specific gravity of the cold air. This current, 
as it passes through, will have an aspirating power to 
draw the air of the other parts of the room toward it. 
This is simply the yacuum-forming tendency which fluids 
always possess when moving. The small arrows show the 
direction of the air in the various parts. Now if the win- 
dow at D be slightly raised, and the one at slightly 
lowered, the vacuum-forming tendency within will initi- 
ate a sufficient current through these openings to supply 
the vacancy. Admitting the cold air at the top, and let- 
ting the foul air out below, seems to contradict the natu- 
ral theory of ventilation as before described ; but it must 
be remembered that here the force of the wind is utilized 
instead of the unequal weights of columns of hot and cold 
air. A further advantage is here realized in the cold air 
being warmed before it strikes the occupants of the room. 

It more frequently occurs, especially in school-houses 
containing several rooms, that the only windows are on 
two adjacent sides. In this case it is generally best to 
make the principal top openings on the side of the strong- 
est wind, and the principal bottom openings on the re- 
maining side. The wind will then after entering be 
deflected by the opposite wall in the direction of least re- 
sistance, which will be toward the largest openings on the 
adjacent side. 

When windows are only on one side of the room, 
the difficulty is still further increased. In this case it is 
generally better to make the principal opening at the top. 



VENTILATION BY WINDOWS. 



67 



and a smaller one at the bottom. The purpose of this is 
illustrated by Fig. 7. When the wind is very strong, the 
upward tendency of the inside air may be counteracted 



Fig. 7. 



Ma 






^ 



-t'r r-r-r-V^r |i^-r-; 



by a large opening at a. The air, being thus forced in, 
will seek the lines of least resistance in escaping. By 
making a small opening at B it will become an outlet, as 
it has less to oppose than at a, where the momentum of a 
large inflowing quantity would be encountered. From the 
laws of fluid pressure it would at first appear that the 
tendency of the outside air to enter at B would be as great 
as at «, and, indeed, even more, owing to the greater 
depth below the surface; but, when it is remembered that 
the relative friction which fluids have to overcome in 
passing through small orifices is so much greater, it is 
plain that in the case of the present example the relative 
absence of friction in the larger top opening gives to the 
wind when passing through a momentum which is suffi- 
cient to establish the current. If, however, the wind is 
of only moderate velocity, the current will be likely to set 



68 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 



the other way — will enter at the bottom, and pass out at 
the top. In this case the size of the openings must be 
suited to the temperature, the number of pupils in the 
room, as well as their capacity to bear hardship. 

When the wind is not strong, and the location of in- 
lets and outlets is not evident, they may generally be 
found by the aid of a feather fastened to the end of a 
pointer, which, held in front of an opening, will indicate 
the direction of the passing current. 

The best possible window ventilation requires the use 
of double windows. Ideal window ventilation would re- 
quire double windows on four sides of the room. Such 
conditions would afford a fair degree of purity. By means 
of double windows the wind may be admitted or kept out 
when and where desired. Its force could be broken by 



Fig. 8. 



' _ ■ ■ ; •■•■•• ■ •■ • ^. ^ ■■ ■ ■ ,.<■■■■ ■ ■■■■ ■■ 



77771 



^ 






t ' ' ■ ■■-.-.>-■---:'■ ■ 



being made to pass perpendicularly between the windows 
before entering the room. Inlets and outlets could be 
made at the top or bottom as required by the circum- 
stances, and the strong drafts unavoidable in single win- 
dows avoided. Fig. 8 illustrates a single case, which, of 



VENTILATION BY WINDOWS. 



69 



course, permits of indefinite modification to suit existing 
circumstances and changing conditions. Here the air 
enters at A by the upper outer window being lowered ; 
descending, it enters the room at B, by the inner lower 
sash being raised; passing over the heater H, it is warmed 
before striking the pupils ; rising, it passes through the 
room, and escapes at 0, by both inner and outer windows 
being lowered. 

Suppose another case, that of a stove situated in the 
middle of the room. Fig. 9 illustrates an instance where 

Fig. 9. 



^^^^^^^^^.^^^^^-.^^^ii^^^^^^^!^^^ 



a 



7\ 



^ 






c 






/ 



V V 



B 



V 



77^ 



^^^ 



H 



• • ''^--"- - ■ - 



^^ 



a single opening serves both as inlet and outlet. By 
making large openings at A c and B D, by loT^ering the 
outside windows and raising the inside ones ; and the 
smaller openings, a and b, by slightly lowering the inside 
windows, it is possible to divide the cold and hot air cur- 
rents, as indicated by the arrows — the chief controlling 
principle here being the unequal weight of hot and cold 
air. Without multiplying instances, suffice it to say that 
in window ventilation the place and relative size of open- 
ings must be conditioned by the direction of the wind, 
the velocity of the wind, and the position of the heater. 



70 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

CHAPTER XL 

ARTIFICIAL YEl^TILATIOlT. 

As distinguished from so-called natural ventilation, 
where the air is changed by means of doors and windows, 
or other openings, the moving forces being the wind and 
the unequal weights of hot and cold air, certain additional 
or artificial means may be used whereby the change of air 
may be made to take place more rapidly, and the regu- 
larity of the movement more certain, than is possible in 
natural ventilation. 

The changes of temperature both in frequency and 
amount are in this country so marked, and the direction 
and velocity of the wind so various and fickle, that even 
the most carefully worked plans for the use of the natural 
methods above described are attended with constant em- 
barrassment and partial defeat. 

Something has been, done toward an intelligent solu- 
tion of the all-important problem of how to measure out, 
warm, and furnish to the occupants of crowded rooms air 
of the proper quantity and quality; but the subject has 
not received a tithe of the attention that its merits de- 
mand. To know exactly how much air is needed by a 
school, and to furnish it by exact mechanical measure- 
ment, is not a very severe problem, and is one with which 
the designers of buildings should be familiar. . To meas- 
ure the amount of water, and estimate its velocity, which 
is necessary to do a certain amount of work, is a problem 
of every-day experience with the civil engineer. Now air, 
no less than water, is matter, and subject to nearly the 
same laws of weight, motion, and measurement ; and to 
manipulate it m the manner required by the conditions 
and necessities of ventilation, providing at the same time 



ARTIFICIAL VENTILATION. 71 

for its exigencies, is an element in school-house construc- 
tion plainly possible, and should be recognized as a part 
of the duty of him who is intrusted with this important 
function. It is as easy to measure air as to measure any 
other substance ; and, owing to its extreme mobility, its 
movement is effected more easily than most other matter. 

The different ways by which this movement may be 
effected may be conveniently considered under two gen- 
eral heads — the vacuum movement and the plenum move- 
ment. 

The Vacuum Movement — Aspirating Chimneys. — The 
act of animal respiration is a pumping or vacuum-forming 
process. As the respiratory cavity is enlarged by muscu- 
lar effort, the air rushes in to fill the vacancy ^bus made. 
Chimneys which serve the purpose of removing smoke 
from a fire, or the foul air from a room, are therefore 
called aspirating, because they imitate in a certain way 
the breathing out of the internal impurities. 

The vacuum-forming power in chimneys, instead of 
muscular action, is the expanding power of heat, which 
lightens the air in the chimney when the outside heavier 
air pushes it upward. The use of the aspirating chimney 
is evident. It is plain that if the air of a room has com- 
munication with a chimney by an opening leading into 
it where the air is hot, rare, and rising, it will be drawn 
out and up to the outside air. 

The velocity of the air-currents produced by natural 
ventilation, described above, can by this means be greatly 
augmented. The utility of downcast shafts for the pur- 
pose of securing pure air is in ordinary natural ventilation 
greatly lessened by the friction which air encounters in 
passing through them : so much so, indeed, that they 
sometimes have to be discarded, being, when the friction 
is in excess of the drawing power, obstructionists instead 
8 



2 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 



of prom^ers to ventilation. By the use of tlie aspirating 
chimney this difficulty may be oyercome. 

In Fig. 10, the fire on the grate G produces an upward 
current through the chimney D. This draws the air 



Fig. 10. 



K^ 





from the tube E, into which the foul air of the room flows, 
through the openings /. The partial vacuum thus formed 
in the room causes the air to flow down the shaft B. The 
downward and upward cast cowls, a and c, described 
above, aid further in facilitating the movement. The 



ARTIFICIAL VENTILATION. 73 

figure is only intended to illustrate the principle. The 
details must, of course, be modified in each case to suit 
circumstances, without violating any of the laws which 
give to the aspirating chimney its main value. 

The main principles which the figure illustrates are : 
the air is taken from an elevated source, it is admitted 
below, and is distributed around the room. It rises and 
passes out naturally at the top of the room into the par- 
tial vacuum made in the chimney by the heat from the 
fire at Gr. The tube E is sometimes carried down to the 
base of the chimney before entering it ; the object of this 
being to prevent the reflux of smoke sometimes resulting 
from sudden changes of conditions, as the wind, rapid 
lowering of the temperature, etc., producing aii;emporary 
reversal of the current down the chimney. This may be 
effectually prevented by adjusting at the aperture H a 
valve V opening toward the chimney. This, when unin- 
fluenced by currents, should hang naturally, closing the 
aperture by its own weight, yielding readily to a slight 
pressure of a current from the direction of the room, and 
closing effectually against a pressure from an opposite 
current, thus shutting off the smoke resulting from down 
draught. This method of removing the foul air was first 
put in successful practice by Dr. Keid in his class-room in 
Edinburgh. The English House of Commons is venti- 
lated on the same principle. 

There are other advantages in carrying the foul-air 
tube directly into the chimney instead of carrying it down- 
ward. The friction resulting from lengthening the tube, 
and the inclusion of two more elbows, would materially 
lessen the draught; furthermore, it has been proved by ex- 
periment that the draught in a chimney is greatest near the 
top, directly under the roof. This may be due partly to 
the increased velocity of the hot air in the chimney near 
4 



74 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

the top, caused by an upward acceleration acquired in 
rising, and partly to diminished resistance to tlie air as 
it nears its point of release from the confining walls of 
the chimney. 

It may at first appear contrary to known laws that the 
velocity of a rising column of air should be accelerating, 
but a moment's consideration will be sufficient to under- 
stand the paradox. Acceleration will always occur when 
a body free to move is acted upon by a constant sufficient, 
as the action of gravity on falling bodies. 

The space passed over in unit time, taken at any period 
of a body's movement, will be measured by the initial 
velocity due to the constant, plus the velocity previously 
acquired. Now, a body which has a tendency to rise will 
accelerate so long as the tendency is constant. Thus, a 
cork, or other light body, in rising from a great depth in 
water, would have a greater velocity when near the surface 
than when it first began to rise. The cause of its rise 
is the difference between the pressures on its upper and 
lower surfaces, but as this difference is always the same, 
whether at a great depth or near the surface, it is a con- 
stant which augments at every instant the velocity already 
attained. 

Montgolfier's formula, v = ^''Igli, is, under the sup- 
posed conditions, as true of rising as of falling bodies — 
remembering that g, instead of being 32 feet, now rej^re- 
sents the distance the body would rise the first second. 
This would, of course, depend on the specific gravity of 
the substance, and would need be determined experiment- 
ally. The case of the air in the chimney is a little differ- 
ent from the one supposed, unless it be that the source of 
the heat be equally distributed along the whole length of 
the chimney. When the source of heat is as usual at the 
bottom, each particle of air loses some of its heat, and 



ARTIFICIAL VENTILATION. 75 

therefore some of its tendency to rise in passing-out ; but 
the retardation due to this cause is slight in comparison 
with the momentum which has been stored up by previous 
impulses. Even this loss of heat may not occur if we are 
to credit the testimony of practical architects. E. E. 
Kice, of Washington, inventor of a system of ventilation, 
says : "I find in practice the highest temperature imme- 
diately below the level of the roof." If this be true, it 
furnishes still further reason for upward acceleration. 

In some systems of heating and ventilating now in 
use the foul-air tubes are carried down and admitted to 
the chimney beneath the fire. It might at first seem that 
this arrangement would give a stronger draught, on ac- 
count of the fact that this air is depended upon to supply 
the combustion in the chimney, but when wholly de- 
pended upon for this purpose the fire will lack much of 
that vigor of combustion upon which the aspirating power 
of the chimney will mainly depend. Air which has already 
been robbed of much of its oxygen, and been contaminated 
with the products of respiration, is a poor supporter of 
combustion. It appears, therefore, that in order to give 
the chimney its greatest aspirating power, the fire should 
be fed with pure air. It is as poor economy to feed a fire 
with COg as to feed pupils with it. Whatever intensifies 
the fire increases the draught. 

The power of a strong upward current of air in a 
chimney to abstract air from tubes opening into it will 
be better appreciated by remembering that some of the 
most effective air-pumps are constructed on precisely this 
principle. An almost perfect vacuum can be made in a 
vessel leading by a tube to another tube through which a 
column of water is falling. In Bunsen's pump, con- 
structed on this principle, water is used ; and in Spren- 
gel's, mercury. In an aspirating chimney the moving 



76 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

current is gaseous instead of liquid, and, although less 
effective, is sufficiently so to create a powerful draught. 
In view of this fact, it might be better in a house above 
one story to carry all the ventilating tubes to a main tube 
extending up nearly to the roof before opening into the 
chimney. 

Owing to the fact that the momentum of columns of 
air is proportional to their volume, aspirating chimneys 
should be built as high as convenient. Where buildings 
are heated by steam, the draught in asjDirating chimneys 
may be created by carrying steam jets into them ; the 
escaping steam causing a partial vacuum, which is filled 
by air coming from below toward the direction taken by 
the steam. See Fig. 11, where C represents the aspirating 
chimney, B the boiler, F the furnace, D the air-duct. 

Fig. 11. 




The arrows show the direction of the current. The steam 
thus issued into a chimney will set in motion a body of 
air about 217 times its own bulk. When steam is used. 



ARTIFICIAL VENTILATION. 77 

the foul-air tubes would perhaps better be placed below 
the jets, as it would in this case be no interference to com- 
bustion, and the chief vacuum -producing power is, in 
this case, where the steam is escaping. 

In buildings furnished with burning-gas, a few jets 
kept burning in a chimney are often sufficient to produce 
the requisite draught. In summer this will be all-suffi- 
cient. General Morin found that one cubic foot of gas is 
sufficient to set in motion 1,000 cubic feet of air. 

Where buildings are heated by steam, it is better to 

run a coil of steam-pipe into the base of the shaft. The 

following formula, deduced by Prof. W. P. Trowbridge, 

may be found useful for determining the amount of 

steam-pipe necessary to be put at the base of an as^^irat- 

ing chimney in order to maintain the desired draught : 

WTa 

S = :pp77^^ ^-7X1,500, where S = number of square feet 

l±(is—ia) 

in exterior surface of the coil at the base of the chimney; 
Ta = absolute temperature of the external air — that is, 
the common or thermometric temperature plus 459*4°;* 
W = weight of air in pounds which is discharged in 1 
second ; H = height of flue ; Ts = absolute temperature 
of the steam in the pipe. The constant 1,500 is deter- 
mined from other constants which were employed in de- 

* The absolute temperature is obtained from the relations which ex- 
ist between the temperature of a body and its rate of expansion. If air 
at 0° C. be heated, its volume will be increased ^-y-3- of its original vol- 
ume for every degree raised. Then its volume will be doubled when 
273° is reached. If it be cooled below 0°, its volume will be diminished 
•2T3- for every degree lowered. If this diminution should proceed at the 
same ratio till — 273° is reached, its volume would be nothing. This is, 
of course, true only theoretically, as it is impossible to freeze matter out 
of existence. But this point is taken as absolute zero, which when used 
makes all temperatures positive. Reduced to the Fahrenheit scale, it is 
459-4°. 



78 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

ducing the formula ; they were : the force of gravity, 
specific heat of air, ratio of transfer of heat to air by 
coils, and the ratio between the theoretical and actual 
Telocity in the flue. 

Steam-coils are used for the purpose here named in 
Columbia College, 'New York, where the heating and ven- 
tilating apparatus was arranged by Prof. Trowbridge. 
They are also used in the Johns Hopkins University of 
Baltimore. 

It is always best when possible to have the ventilating- 
flue combined with the smoke- chimney, so as to utilize 
the heat of the waste products of combustion. When 
heat from this source is insufficient, it can be supple- 
mented by the use of the steam-coils. 



CHAPTER XII. 

THE MOVEMENT OF TFE AIE BY MECHANICAL MEANS. 

The Vacumn Movement. — A current of air through a 
room for the purpose of ventilation is sometimes produced 
by putting into the ventilating or foul-air duct an extract- 
ing fan, Archimedean screw, pump, or blower. Such an 
arrangement may take the place of an aspirating chimney, 
or by being put into the chimney become a part of it, sup- 
plementing its draught-producing function. The func- 
tion of mechanical propellers, when put in the foul-air 
duct, is always the same, that of producing a partial 
vacuum in the room by extracting the foul air, thus 
making room for a fresh supply, which will find its way 
in by openings provided for that purpose. 

When mechanical means are thus made use of, it of 



MOVEMENT OF THE AIR BY MECHANICAL MEANS. 79 

course makes no difference, in tlie rapidity of change 
which the air in the room will undergo, whether the pro- 
peller be placed in the foul-air duct and draws the air 
through the room, or whether it be placed in the fresh- 
air duct and pushes the air through the room, for in 
either case the propeller moves the same quantity of air. 

Whatever is forced in must find a way out, and what- 
ever is drawn out must be supplied by inlets. When air 
is thus drawn out, it is a vacuum-forming process, and 
the pressure of air on the inner parts of the room will be 
somewhat less than that on the outside. Currents of air, 
therefore, through small openings, cracks, windows, as 
also from halls, closets, etc., will be inward ; the quality 
of the air, therefore, will be determined by the character 
of tlie inlets, and the function of the intended^inlets may 
be usurped by an open door delivering air too cold, an 
open closet delivering impure air, or an elevated crack or 
other opening delivering air too high up to be utilized, 
and so drawn out unused. 

Another objection to this manner of drawing the air 
through the room, especially where the draught is from 
several rooms, is that the draught will not be equal. In 
rooms which have their inlets through tubes compara- 
tively short, where the incoming air encounters very little 
friction, the supply will be ample and at the expense of 
more remote rooms to which the air must pass through 
long tubes and perhaps j)ass abrupt angles. The relative 
draught will also fluctuate with changes in the force and 
direction of the wind, sometimes favoring one side of the 
house, sometimes another. 

The Plenum Movement. — Instead of drawing the foul 
air from the room by placing the propeller in the exit 
shaft, the pure air may be forced in by placing the pror 
peller in the inlet duct. This may be called the plenum 



80 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

movement, and produces in the room a perflating instead 
of a vacuum-forming tendency. 

The plenum has many advantages over the vacuum 
movement. In this movement the atmospheric fullness 
in the room, produced by perflation, causes all currents 
through accidental openings to be outward instead of 
inward, thus preserving the air of the room from the 
incidental external impurities of closets, cellars, base- 
ments, etc. 

The plenum movement has not received the attention 
which its usefulness demands. Much as may be said in 
favor of natural ventilation, and evident as it is that all 
successful ventilation must depend on a studious and 
skillful conformity to the few natural laws underlying 
the whole process, it will still remain questionable, after 
everything possible has been done to produce draught 
by differences of height and temperature, whether it 
is possible to supply at all times a large school-house 
full of pupils with air of the necessary quantity and 
quality. 

We have seen in preceding pages how fast air must 
pass through a room in order to supply the requirements 
of respiration. We have also seen that this current must 
be properly distributed and be of a certain temperature 
and humidity. Now these conditions are approached in 
different degrees by different systems of heating and ven- 
tilating ; but in no system lias the ideal teen reached 
without the aid of mechanical means. 

There are many good systems now in use, the in- 
ventors of which deserve great credit for much good 
work toward solving the great problem of warming and 
ventilating. But the efficiency of none of these systems 
is quite commensurate with the claims of their inventors. 
The comparative merits of some of the best systems now 



MOVEMENT OF THE AIR BY MECHANICAL MEANS. 81 

in use are discussed in another place, where the prin- 
ciples involved in each are examined. 

The assertion which I here venture, that perfect 
warming and ventilating has not been attained without 
the aid of mechanical means, is easily demonstrated on 
general principles. What is implied in perfect ventila- 
tion ? As an example of it, we might suppose the case 
of a balmy spring day, when a gentle breeze, barely per- 
ceptible, is passing through the wide-open opposite win- 
dows of a room situated in a salubrious locality. In this 
case the air is of a genial warmth. It has not been blown 
across a burning desert or through an artificial furnace. 
It does not enter the room scorching hot, where it mixes 
with other air icy cold. It is not kept in the room till it 
has become dangerously impure ; but in passing directly 
through it gathers the impurities of the passing breath 
and carries them away as fast as formed, leaving the 
room while still in a state of respirability. 

Now this may be produced artificially, by warming 
the air to the proper temperature and forcing it through 
the room by mechanical means, but by any other means 
now in use it is impossible. A little reflection will make 
this plainly evident. 

We have previously seen that when adequate ven- 
tilation is maintained by an upward current through 
the room, it is caused mainly by the difference between 
the internal and external temperatures and the vacuum- 
producing power of aspirating chimneys. But how is 
this difference of temperature in very cold weather to be 
produced ? If by stoves, the temperature in different 
parts of the room will be unequal — some parts hot, and 
other parts cold ; if by the direct radiation of steam 
pipes, the entering air is cold, and, although it be warmed 
by passing over the heater, it will be warmed unequally 



82 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

and imperfectly. If by warm air entering the room, it 
must enter fast enough to change the air in the room 
about every seven minutes ; but air of this temperature 
vy^ill not enter thus rapidly by any ordinary medium of 
pipes and tubes, on account of friction, etc. 

The main cause of the inflow of the warm air is the 
difference of its specific gravity due to heat. For the 
inflow to be rapid the heat must be great, but hot air 
must be ruled out of the legitimate conditions of j)erfect 
ventilation. It is, I think, possible to pass air not above 
a temperature of genial warmth when it enters, in suffi- 
cient quantities to serve the ends of ventilation, and 
sufficiently to warm the room in cold weather, but it re- 
quires a different arrangement of pipes and furnaces than 
has yet been put in practice, and might exceed in cost a 
good plenum movement. 



CHAPTEE XIII. 

AIR-PKOPELLEES. ' . 

The problem of setting in motion quantities of air 
sufficient to supply the requirements of ventilation, and 
to so direct this air as to approximate a maximum of 
movement with a minimum of expended power, is a me- 
chanical problem which becomes important in considering 
the plenum movement, both from the standpoint of work 
accomplished and the economy of accomplishing it. 

Of propellers for moving air, many kinds have been 
used, among which may be mentioned those of Combs, 
Eittenger, Hales, Letoret, Howorth, Eoots, Glepin, Ar- 
nott, Chaplin, Perrigault, Lloyd, Fernie, Hendry, Hope, 



AIR-PROPELLERS. 83 

and Blackmail. Most of these are in some form of revolv- 
ing fan, the floats of which are so j)laced as to set in motion 
the air outward radially, thereby creating a partial vacuum 
near the axis, thus setting more air in motion as it is filled. 
The object of a propeller is not only to set in motion 
large quantities of air, but to set it in motion in such a 
manner as not to produce loss by opposing counter cur- 
rents and by useless friction. Air, on account of its ex- 
treme mobility, requires primarily very little power to 
move it, but when it is forced through small apertures, 
or set in motion in such a way as to produce cross cur- 
rents, great power may be required to accomplish a little 
work. Dr. Arnott observed this in the working of re- 
volving fans, and invented a ventilating pum;^^ which he 
put in operation in a hospital. So conserved was the 
power by the construction of his propeller that the entire 
building was supplied with air by the motive power de- 
rived from the descent of the water used in the building 
from a high reservoir to the basement. It may be re- 
marked here that everything which Dr. Arnott devised for 
the improvement of ventilation possessed singular and 
unusual merit.* Since Dr. Arnott's time, however, con- 
siderable improvement has been made in revolving fans 
and other propellers. 

* As before mentioned, Dr. Arnott never secured the exclusive right 
to his inventions by letters patent, but in a true philanthropic spirit 
gave the results of his labors to the world. It is doubtful, however, 
whether this did not hinder rather than promote the propagation of his 
ideas. It is noteworthy that while these inventions are acknowledged to 
be superior to most others, and are free to everybody, they have been 
comparatively little used. Had the worthy author secured his inventions 
by letters patent everybody would be ready to scrutinize their merits and 
pay the price ; but when a gift is offered it is little regarded, so prone 
is human nature to think it impossible for a man to give away that which 

is of value. 
9 



84 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 



The objection which has heretofore been made to the 
plenum movement is its expense. Owing to the extreme 
mobility of air, the power required in merely moving it is 
theoretically almost nothing ; the expense, then, must 
result from the manner of moving it — from forcing it 
through small apertures, and from friction and collision 
due to misdirecting it. The construction of the machines 
for propulsion is, therefore, of so much importance in 
the economy of mechanical ventilation that I shall notice 
at some length the construction and efficiency of some of 
the earlier and later types of revolving propellers. 

Rittenger^s Fan. — Fig. 12 represents Rittenger's fan. 
A is a side view showing the shell y, which is of the form 

Fig. 12. 




'^^^^c^^ ^m^^^i ^i^^iii^i^i^^^^^^^ 



of an Archimedean spiral, beginning at e ; the radius of 
the inlet r2, the outer and inner radii of the vanes r and 
r^, the radii I of the curve of the vanes ; the angle z° be- 
tween the radius and the initial line of the vane. B is a 
section on the line xx\ The arrows show the direction 
of the current, 



AIR-PROPELLERS. 35 

The construction of this fan shows that its design is, 
first, by the angle z, to i^roduce a motion of the air ra- 
dially, producing a vacuum-forming tendency at the cen- 
ter, causing the air to be pushed in toward that point 
from the outside ; and, second, by curving the vanes 
forward, to direct the tangential motion of the air as far 
as possible toward the outlet duct. 

To understand the action of the vanes on the air, sup- 
pose a single particle of air at ^ struck by the vane as it 
reaches that point in its revolution. If the angle z"^ were 
0, then the particle would be impelled forward on the 
tangent p';?; but as the angle 2;° increases, the direction 
taken by j9 will be more radial, the amount of this change 
of direction being proportional to the sine of 2;°, the rela- 
tion holding between and 90". If the vanes Be straight, 
increasing z will give the air a receding tendency ; this 
the curve is intended to prevent. Now, the nature of 
this curve is of course important. Its radius of curvature 



r? 



IS expressed by Eittenger by the formula 1^=^ — . ^, 

where r = outer radius of the vanes, r^ = inner radius of 
the vanes, z"^ = the angle between the radius and the 
initial line of the vane, and I = radius for the curvature 
of vanes. The formula shows that as the vanes are nar- 
rowed, or as r' — - r^ is diminished, I will decrease. Eefer- 
ence to the figure, with a little mechanical conception, 
will prove the general correctness of these relations. For, 
if we imagine r^ to be increased, thus narrowing the fan, 
the particle of air jo will have its distance from the shell 
diminished, so that when deflected radially by increasing 
2;° it would have a sharper curve to give it the required 
forward impulse than when it started from a greater dis- 
tance, giving more time for deflection. 

The formula shows, further, that as sine 2;° (or 2;°) is 



86 VENTILATION AND WAKMING OF SCHOOL-BUILDINGS. 

increased I will be diminislied. Eeferring to the figure 
again, the reason becomes evident. For as z° is increased 
the particle of air p will be deflected more radially ; to 
counteract this before the circumference is reached the 
curve must be made sharper — I must be lessened. 

The effect which in this fan is realized in practice is 
about forty per cent of the power expended. Yet this is 
one of the best fans which have been thoroughly tested. 
Surely there is an open field in the economy of applied 
power for the mechanical engineer. 

In this fan, it appears to me that much of the loss of 
effect comes from beating the air too much radially, and 
not enough tangentially ; or, rather, that the radial and 
tangential forces are not properly distributed. In this 
case the direction of the impulses is too much outward 
on the shell, and not enough forward toward the duct. 
Now, this can be partially corrected in making the curve 
of the vane elliptical instead of circular, where each vane 
comprises one fourth of the ellipse. I would therefore 

propose the following modified formula : I = ^ • a , 

2 r^ sme z 

where I = semi-major axis of the ellipse, e = the ratio be- 
tween the major and minor axes, and r, r^, and z"^ = same 
as in the preceding. This relation shows that e increases 
with the width of the vanes, and also with the length of 
the semi-diameter of the curve. 

The amount of work which is required to deliver any 
given amount of air by means of fans may be calculated 

1, x-u . 1 TT 62-5 100 ^^/ , ^ 

by the formula Hp. = — - x X V h, where Hp. = 

number of horse-powers, 62 -5 = weight of a cubic foot of 
water, 550 = number of pounds in one second by one 
horse-power, x = per cent of efficiency, V = volume of 
air delivered in cubic feet per second, h = the relative 



AIR-PROPELLERS. 



87 



weight of the air compared with an equal bulk of water. 
As the air is denser than normal when being forced 
through the ducts, h must be determined by the ma- 
nometer. V can be found by means of an anemometer. 
(See Appendix C.) 

Coinbs^s Fan is of different construction, but as its 
per cent of efficiency is somewhat less than that of Kit- 
tenger's it will not here be discussed. 



Fig. 13. 




88 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

Blachman^s Fan (see Fig. 13). — As an example of mod- 
ern impro Yemeni in revolving fans, I copy from the 
patent-office specifications the description of what seems 
to me one of the best yet constructed (see Appendix F). 

The Hope Fan. — An improvement on the Blackman 
Fan has recently (1886) been patented by Hope Brothers, 
of Kansas City, Missouri. The improvement consists of 
a slight modification of the vanes, and the conversion of 
the whole fan into a water motor, which is the power 
used. 

This fan motor undoubtedly possesses some advan- 
tages over any other yet devised. It can be used either 
as an exhauster or a perflator, and, by being placed di- 
rectly at the entrance into the room, the loss from fric- 
tion of moving air through long ducts is prevented. By 
api^lying the power at the circumference of the wheel, 
instead of near the center, as is usual when belting from 
an engine, much power is gained, especially when a rela- 
tively small quantity of water is used under high pressure. 

Of course, when other things are equal, no gain would 
be realized by applying the power at the circumference, 
as what is thus gained in power would be lost in velocity, 
but in the case supposed, where a small stream of water 
under high velocity is used, much of the effective power 
will exist in its vis viva as it strikes the buckets. Now, 
as the vis viva is proportional to the mass of the moving 
body, and to the square of its velocity, the increase of 
velocity will be more effective than an increase of mass. 

One of these fans is adequate to move the air of a 
school-room of ordinary size. It can be run for five cents 
per hour, as proved by actual experiment in Kansas City, 
when the water pressure is eighty pounds. 

Patent of Hendry and Others. — One of the most ad- 
vantageous arrangements is to put the fan in the angle of 



AIR-PROPELLERS. 



89 



the shaft and ventilating duct,- as illustrated in Fig. 14. 
The advantage gained in this arrangement consists in car- 



FiG. 14. 




B 



rjing the entering air only one fourth of a revolution be- 
fore releasing it. 

In the figure, the arrows show the direction of the 
fan's revolution, and also the direction taken by the air. 
As the vane a is moving forward in its present position it 
carries in front of it the air in the lower part of the shaft 
A ; the tangential motion which the revolution gives to 
this air will, when one fourth of a revolution has been 
made, send it through the duct B. This manner of plac- 
ing the fan is used by A. J. Hendry, of Georgia, in an 
invention patented in 1883. The amount of friction 



90 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

which this arrangement obviates would allow the use of 
clock motors which could be wound up at stated inter- 
vals. A shaft and tube could be supplied each room, and 
the motors thus distributed would furnish ample power 
for propulsion. 

The plenum movement, so far as at present attained 
in practice, will deliver from fifty to one hundred and 
fifty cubic feet of air per horse-power per second. But 
these estimates have been made irrespective of accompa- 
nying effects of natural ventilation. In arranging for the 
plenum movement every provision should also be made to 
derive all possible aid from natural movement. When- 
ever it is possible to ventilate by natural means, the me- 
chanical means could be suspended. It should be the 
object of the plenum movement to supplement the natu- 
ral, not to replace it. By working with Nature as an aid 
the amount of power required would be greatly lessened. 



CHAPTER XIV. 

CAl^ THE PLEKUM MOYEMEN^T BE AFFOKDED ? 

liT order to answer this question understandingly it 
will be necessary to enter into somewhat lengthy detail 
concerning the amount of heat needed, the amount of 
unavoidable waste, and the amount of fuel necessary to 
the supply ; then to consider the cost of adding thereto 
the cost of the plenum movement, and to compare the 
total estimate thus made with present expenditures. 

In making these estimates I shall consider a single 
room, of average size, and supposing the average conditions 
as to exposure, number of windows, locality, etc. The 



CAN THE PLENUM MOVEMENT BE AFFORDED? 91 



Maximum number of 
degrees tempera- 
ture to be raised. 



Average number of 
deftrees tempera- 
ture to be raised. 



CO 00 CO CO 00 CO 1 



s<3(?<ooeo ooooeocor-isorreocjiw 



Mean temperature of 
tire months. 



»rc5j:-in(Min(?»NQO»oao->-ioi~tMo:i^ooooeoco{~»ooofO 
00 CO CO CO CO CO »n -^ CO CO o* -^ oo^coco ■^ ■r}< co co iO co a* -^ »n •^ 



No. of months fire is 
required. 



t- O i.- CO i> J.- CO t- i> £- M i> O q5,tD i«CX)OJ>i>t^QO'»4<iOt-»n-<J'5D 



Mean. 



Minimnm. 



QO-i'00-^C5i-i'<*<i>l-Ol~T-i'NCirJ'eOi.--COCOT-<-5r'-i->"3:l-S-. {- 

g< coco co_o« at JO CO cQg^ lytoo t^co oo ■rre^ia c ococo o jioooi- ioo j^^ cc 

t^ 1-1 1-1 » 00 '■* CO ?0 O CSOlO'^'^OOOCSQClJl-^OINCSlOt- CO iC I- 
1-4 T-t i-ii-i(M COi-i-^ 1-1 Oi 1-1 CO (M 1-11- 



Mean. 



Minimum, 



oio(MOiooQO«3ao-^c;c<C'icoo>o-^oi-GOQO:o-ri-i-roxi- 

T-<T-I T-( (N C* O i-l»<i-iCO i*i-lTJr-lC\J!JJ 



Minimum. 



Minimum. 



Mean. 



l^l 



1 1-1 iofcoo 5 

■ t- O I! I- t- i 



Minimum. 



J o: oc o loco ' 
) -rr -^ m m -^ I 



[Mean. 



>S Minimum. 



Mean. 
Minimum. 



Mean. 



Minimum. 



{Mean. 



1 1- ■r)"* m "* < 



' "-W '*■« ^I" ^.-j Jl- -^z 

) TC CO si CO 00 CO 



I m »;: CO in CO I 



Mean. 



'i-ioooi~C5ao»nx)coc5i 

[ 1-1 1-1 1-1 1-1 CO i-c rH 1-1 < 

1 1-1 oi~o^ ?>. m -t T> ; 



' Til -* o 5* I- 
! 1-1 1-1 ■<*> W 



Minimum. 



CO 00 CC CO CO CO CS " 
^O (N CO 1-1 lO 00 ( 



5 -r CO CO I 

io*--sxco;cao05CJi-ii 



> -J o* --s X ! 



P^ 



) 5^ Q* '?»«-» »ft f 



;OOtj<CJC5iOS5C:0-- _-i 

1-1 CO i^ <?* CO -^ ■?? o CO CO CO g< 'ra C0 1 



Miuimum. 



_>-^oo«oo50co'MC'»i-(»-'Oi-i-ieo2Ji*''5l'' 
;^" "r^wi-^oi .i-HMco ,io , i-ic*oo rH Tj« .c<? .1-ioj 

I I I I I I I I I I II I I I I I 



iT 



Mean. 



0\! CO '^^ 5< Si oj iC ! 



) X X I- >n >n :£ o ' 

! O TJ CO ■^ "M O CO ! 



Minimum. 



I I I I I I 



: O O O OJ ift ' 
nn<?* 1-1 <N I 

I I I 



I I 






CSX3 



o ^• 



"Si) Pj'S 

moo 






_" r; -^ — .. <-■ -'^ <u 
boaQ^WH:i^^<i!^l^ 



:o 



:00 



.2 ,s5c?^u: SCO 
•S-^ o -'^2 5 , 
3 cf-s e .22 „' tc bed" 

"O^ «>• O 55-;= •= 53 
«xT3'*i-3P-i'3_a':3 

!g . - o 5 *i -i^' >^ i;r o 



92 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

table on page 91 shows the minimum and mean tempera- 
tures of each month, compiled from observations of the 
Signal Service, U. S. A., and Blodgett's ^'Climatology of 
the United States." As the table shows, the amount of 
heat required depends partly on the latitude and locality 
of the place. I select for our estimate that of Chicago, as 
representing a high average, but, of course, at places far 
north or south, other figures will be found in the table 
which will be more appropriate. 70° is taken as the tem- 
perature of comfort, and to which existing temperature 
must be raised. Taking seven as the number of months 
fire is required ; the average temperature of these months 
35° ; then the average number of degrees of temperature 
to be raised will be 70° — 35° = 35°. Taking the average 
number of pupils in one room as 60, the cubic feet of air 
required in one hour will be 60 X 3,000 = 180,000. A 
thermal unit, or unit of heat, is the amount of heat re- 
quired to raise one pound of water one degree. By careful 
experiment and comparison of the specific heats of air and 
water, it is established that this amount of heat — one 
thermal unit — will raise 48 cubic feet of air one degree. 

Then — '— — = 3,750 = number of thermal units neces- 

48 

sary to raise 180,000 cubic feet of air one degree, and 
3,750 X 35, the average number of degrees to be raised, 
equal 131,250, the number of thermal units necessary to 
supply the occupants of one school-room one hour. 

Loss through the Walls. — The formulas which it will 
be necessary to use in making these estimates may seem 
difficult, but they have been deduced from well-known 
laws and properties of matter familiar to every physicist, 
and formulated by the best European mathematicians. 
They are in practical use by skilled engineers everywhere. 
The loss of heat through walls, when all sides of the build- 



CAN THE PLENUM MOVEMENT BE AFFORDED? 93 

ing are exposed, may be calculated from the formula U = 

, V , , . — r- — l^ , where U = total units of heat lost per 
C (2 h-\-r)-\-ekq 

hour per square foot ; h = loss by contact of air for a 
difference of 1° = -4912 when the air is moving ; C = con- 
ducting power of material (see table, Appendix D, page 
167); r = radiating power of material (see table. Appendix 
E, page 168) ; q =:r -\-h; T = temperature of air in the 
room ; T^ = temperature of external air ; e = thickness of 
wall in inches. The loss of heat through floors and ceilings 
when not exposed to the external air is usually regarded 
as null. Taking 26 feet X 34 X 14 as the size of the 
average school-room, 120 X 14 = 1680, area of walls in 
square feet. Counting six windows, each 9 X 3|- feet, 
9 X 3J X 6 = 188, area of windows ; 1680 — 188 = 1492 
square feet of wall surface. The wall is supposed to be 
18 inches thick. 

The values in this example to be used in the above 
formula will be U = -4912 ; c = 4*83 ; q = r-{-h= -7358 
+ -4912 = 1-227 ; r = '7358 ; e = 18 inches ; T = 70° ; 
T, = 35°. Then 

'49 12X4-83X1-227X35 __ 101-8 8__ 

4-83 (2x4-912+-7358)+18x4-912xl-227~ 19-13 "* 
5*32 = thermal units per square foot per hour; 5-32 X 
1492 = 7937-44 = thermal units lost through the walls in 
one hour. 

Loss through Windoivs. — When the windows are not 
more than J inch in thickness the following formula is 
used for finding the value of U : TJ = 5^ (T — t^, where 
t^ = temperature of the glass ; q=z r -{-h'^ r = radiating 
power of the glass ; U = loss by contact of air for a differ- 
ence of 1° = -4912. 

The values in this example are, q = (r -\-h) =^ (-5948 
-f -4912) = 1-086, T = 70° ; jf, = ^V- = 1^'^ ; ^^^cn U = 



94 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

1*086 X 17*5 = 19 = thermal units per square foot. 
Area of six windows = 188 square feet x 19 = 3572 = 
loss through the windows in one hour. 

Total Loss. 

From incoming fresh air ...;.. 131,250 

From walls 7,937 

From windows 3,572 

Total thermal units 142,759 

Now, in the burning of one pound of coal 13,000 ther- 
mal units are evolved. The efficiency of a heating appa- 
ratus depends upon the amount of surface exposed and 
skill in firing. In practice, the efficiency of heaters is 
from 38 per cent to 80 per cent of the whole heat evolved. 
Taking 60 per cent as a fair average of efficiency, 

142,759^ 100 ,^_, , - . „ , 

^ , ' _ X -^7r= 18*3+, number of pounds oi coal re- 
lo,000 oO 

quired for one room for one hour. From this as a unit the 

cost for a building of any number of rooms may be obtained. 

For example, counting seven the number of fire 
months, eight as the number of hours per day in which 
fire will be needed, $5 the price of a ton of coal, the cost 
of heating a building of ten rooms would be, 
18-3 X 20X7X8X5X10 ^ ^ ^ 
2000 * 

Now, under the conditions supposed, this will be the 
necessary expense ; any less would imply that the chil- 
dren and teachers are fed on impure air. To heat such 
vast quantities of air as the conditions of sufficient venti- 
lation necessitates requires large expenditures of heat. 
There is no help for this. The rations of pure, life- 
giving air measured out to children shut up in close 
houses should be as. certain a quantity as the daily allow- 
ance of bread and butter. 



CAN THE PLENUM MOVEMENT BE AFFORDED? 95 

By examining reports of school boards from various 
cities I find that the expenditure above calculated is 
not far from the actual average cost of supplying such 
school-houses similarly conditioned. That is to say, the 
present expenditure for fuel is sufficient to supply the 
most rigid demands of sanitary ventilation. 

We are not ready, however, to conclude that all is 
well. The coincidence of these facts proves nothing. 
There would have to be an important additional element 
to make these two first facts possess a causal relation to 
each other. If the school expending this amount of fuel 
should be visited by an expert who, after examining the 
air, testing for 00a and noting the rate of renewal, found 
that the air was being renewed every six to sevens minutes, 
and the 00a not above '2 per 1000 of air, then the con- 
clusion would follow that the expenditures had been made 
economically. 

But, unfortunately, this important third element is 
wanting. The real facts are too well known to admit of 
any mistake here. Instead of the air of the average 
school-room being changed every six minutes, it is not 
changed oftener than once in thirty minutes, and more 
frequently probably not oftener than once per hour. In 
thousands of houses it is not changed at all, just enough 
air working its way in by diffusion to prevent immediate 
deatti by suffocation. 

These are the facts. It would be tedious to enumer- 
ate the commissions which have from time to time in dif- 
ferent parts of the world been appointed to investigate 
this subject. While there is variety in the character, 
number, and locality of these investigations, there is 
singular unanimity of results. The invariable verdict 
of all may be epitomized as bad, bad, BAD ! Some are 
better than others (or, rather, some are not so bad as 
10 



96 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

others), but the difference is rather in degree than in 
kind. 

The question which now confronts us is, What became 
of the heat from all of that coal ? There is but one an- 
swer : It was wasted. There may be many sources for 
this waste. Windows and doors are thrown open to re- 
lieve the temporary inconvenience of a depressing atmos- 
phere. These openings, especially when near the heater 
or incoming warm air, at once become outlets, setting 
the current toward them, and drawing out the warm, 
pure air as fast as furnished. 

Too small heating surfaces or unskillful firing may 
also be causes of waste. Overheating the air and con- 
fining in the top of the room (as is the practice of some 
hot-air systems) till it cools down to the temperature of 
comfort is a positive waste by conduction through the 
upper walls and windows. The only way to utilize the 
excess of heat in supra-heated air would be to thoroughly 
mix it with such an amount of cold air as would be re- 
quired to reduce the temperature to that of comfort. 

In view of this state of the case, what is the remedy ? 
How is the heat which is being expended to be utilized ? 
The answer is evident. There must be some means 
whereby the air in a room may be changed with requisite 
frequency, and this independent of the doors and win- 
dows. The heating surface must be properly propor- 
tioned to the amount of fuel consumed in order to lessen 
the waste through the smoke chimney. Air must not be 
heated much above the temperature at which it is to be 
used, in order that there may not be loss in cooling. 

We return now to the original question. Can the 
plenum movement be afforded ? Can the extra expense 
of moving this air through the building be assumed by 
the people ? This, it seems to me, is much like the 



THE COST OF VENTILATION. 97 

question of a man who, after having paid a high price for a 
stove, asked his wife if they could afford the coal to build 
a fire in it. Not to provide the means of utilizing ex- 
pense already incurred is simply to waste this expense. 

I am aware that many economize by an exact count 
of dollars and cents concerned in immediate expenditures. 
But to this question true economy has but one answer : 
This air must in some way be moved. If it can be done 
by aspirating chimneys, of proper size and construction, 
very well ; if not, it must be moved by mechanical means. 
At all events, it must be moved by some means. 



CHAPTER XV. 

THE COST OF VENTILATION. 

Cost of the Aspirating Chimney. — Let us approximate 
the cost first of the aspirating chimney. We have seen 
(see Appendix B) that where the fresh-air inlets are of 
adequate area the velocity of the air in the ducts should 
be at least 7*7 feet per second, say 8 feet. Assume the 
height of the aspirating chimney to be 70 feet. 

To find the sectional area of an aspirating chimney 
which is to take away all the air that passes in one hour, 

Y 
we have A = _^ ^^^ , where A = the sectional area of the 
oD,OOU V 

aspirating chimney ; V = volume of air passing through 
the chimney per hour ; v = velocity of air per second in 
ducts ; 3,600 = seconds in one hour. Then the sectional 
area of a chimney required for a single room in our exam- 

,1 -A 180,000 ^ ^ f L rvu ^r. 

pie above is A = - = 6-2 square feet. The ve- 

O;,o00 X t> 



98 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

locitj of the air will depend upon the difference of tem- 
perature between the air in the chimney and the air 
outside. 

Now, the number of degrees temperature which the 
air in the chimney will have to be raised in order to 
produce a velocity of 8 feet (or other given rate) may 

v^{l+et){l+f-^+f,) 
be formulated : t„ = ~ (^i ~ 0^ 

where t^ = increase of temperature by fire ; v = velocity 
of air in feet per second in ducts ; e = expansion of air 
per 1° temperature = '00203 ; t = external temperature ; 
/= co-efficient of friction in ducts ; I = total length of 
ducts ; d = diameter of ducts ; ti = internal temperature 
of room ; g = accelerated gravity ; h = height of chim- 
ney ; /i = co-efficient of friction in elbows. 

The corresponding values in our example are : v^ = 
8' = 64 ; e= -00203 ; t = 3o°;f='06 (for rough flues) ; 
/i = 4 '5 (assuming three square elbows, which is proba- 
bly a fair average) ; I = 180 (this includes the height of 
the chimney, the height of the pure-air shaft, and the 
ducts) ; 180 is a fair average ; d= 2'5 (for estimate made 
on necessary size of total inlets, q. v.) ; g = d2'16 ; h = 
70 feet ; ti = 70°. Substituting these values : 

64 (1 + -00203 X 35) f 1 + -05 \^-^ + 4-5) 

/ = 1 i*.5 ^ - 35 = 

^ 2 X 32-16 X 70 X '00203 

-^-j^g- - 35 = 33 35 . 

The quantity of coal necessary to produce any given 

t sW 
temperature is expressed K = ^ , where K = number 

of pounds of coal per hour ; s = specific heat of air = 
•238 ; W = weight of air in pounds carried off per hour ; 



THE COST OF VENTILATION". 99 

11 = units of heat utilized in one pound of coal when 
burned on a grate = 6000 ; ^ = per cent of loss by radia- 
tion through wall of chimney = '9. 

Present values : t^ = 33-35° ; s = '238 ; W = 14,400 
pounds (weight of 1 cubic foot of air at 35° being '08, then 
180,000 X -08 = 14,400) ; ^ = -9. Substituting : K = 

33 -35° X -238 X 14,400 ^, ,, , „ . „ 

^-7-Tx ' = 21, the number oi pounds oi 

5,400 

coal necessary to burn per hour on a grate in the chimney 

in order to secure sufficient ventilation. 

This, it will be observed, is more by nearly 3 pounds 
per hour than was found to be required for heating. 
Evidently, then, coal burned on a grate in an aspirating 
chimney, for the purpose of creating a draft, is |xpensive. 
Can it be afforded ? If there were no better way to ac- 
complish the same work there would be but one answer : 
Yes, of course, it can be afforded, for the children and 
teachers must have air. 

But this sui)posed expense is not necessary. Instead 
of heating the aspirating chimney, as heretofore described, 
it may be combined with the smoke chimney, which will 
generally, if properly constructed, be sufficient to heat 
the aspirating chimney to the required degree. This 
may be done, has been done, in various ways. The foul- 
air ducts may lead to an aspirating chimney built around 
the smoke chimney so as to be warmed by it. They may 
open directly into the smoke chimney, either above or 
below the fire, or they may be carried up to near the top 
before entering. On account of a possible tendency to 
smoke in windy weather, it is probably best to have the 
chimneys so arranged that the heat from the smoke chim- 
ney may be utilized in the aspirating chimney without 
direct communication between them internally. To effect 
this, I would suggest that the smoke and escaping heat 



100 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

from the heater be carried off through a large number of 
small metallic tubes extending up through the chimney. 
The large surface thus exposed to the air inside the chim- 
ney would thoroughly heat it to the temperature required 
Id an aspirating chimney. 

In Fig. 15, represents the wall of the chimney ; F, 
the furnace ; the lower arrows, the course through the 

Fig. 15. 




tubes taken by the smoke ; D, the foul-air duct leading 
from the school-room ; the tipper arrows, the course be- 
tween the tubes taken by the foul air. A number of 
small-sized stoye-pipes would answer well for the tubes. 
In this case the chimney would have to be made large 
enough, so that a cross-section of the chimney, minus the 
sum of the cross-sections of the tubes, would leave a 



THE COST OF VENTILATION. 101 

remainder equal to the required size of au aspirating 
cliimney. 

The main trouble with aspirating chimneys has been 
from making them entirely too small. We saw above 
that the sectional area necessary for a single school-room 
is over 6 square feet. Calling it 6, then, for six rooms, 
it would be 36 square feet — 6 feet square. For eight 
rooms, 48 square feet — nearly 7 feet square. For four- 
teen rooms, 84 square feet — over 9 feet square. In the 
arrangement above illustrated the necessary area for 
smoke-flues must be added to these numbers to obtain 
the size which the chimney would have to be built. 

To calculate the area of smoke-flues, engineers usually 

use the formula A = '128 — ^:=r , where A = sec^onal area 

in square feet ; K = pounds of coal consumed in one 

hour ; '128 = a constant ; h = height of chimney in feet. 

The corresponding values in the present calculation 

are : K = 18-3 : ^ = 70. Then A = -128 -^ = -279 

V70 

square feet = '279 X 144 = 40*1 square inches. We found 
above that the necessary area of an aspirating chimney 
for one room is 6*2 square feet = 892*8 square inches ; 
40*1 inches being -044 of 892*8 square inches, the en- 
tire size of the chimney, including smoke- and foul-air 
flues, may be found by multiplying the necessary aspirat- 
ing chimney area by 1*044. Then 6*2 square feet, the 
area of an aspirating chimney for one room, multiplied 
by 1*044 = 6*472 square feet. This is sufficient to show 
that the chimneys, when intended for the double purpose 
of carrying smoke and foul air, must be large and high. 
On this account, where there are more than six rooms in 
the same building, it is better to have two chimneys. It 



102 VENTILATION AND WARMING OF SCHOOL-BUILDINGS, 

thus appears from tlie foregoing that, by a properly-con- 
structed aspirating chimney, yentilation may be, under 
favorable conditions, secured without additional cost for 
fuel. The attendant unfavorable conditions will be no- 
ticed presently. 

Cost of the Plenum Movement. — No\v, to calculate the 
cost of the plenum movement : If the Kittenger fan be 
used, and calling its per cent of efficiency 40 — the value 
of X in formula for estimating Hp. (see page 86) — we 
have Hp. = '28 V h. (h = height of manometer). In the 
present example V = 180,000; h= -08 (taking the av- 

, ^, ^^ -28X180,000 X -08 ,, 
erage). Then Hp. = j^ = I'l, say one 

horse-power for each room. In practice, it requires from 
5 to 8 pounds of coal per horse-power per hour, so that 
the cost of moving the air by mechanical power would be 
about one third of the cost of heating. 

This estimate is made without reference to recent im- 
provements which have been made in fans and blowers 
for moving air more economically. The efficiency of the 
Blackman fan is doubtless as much as 70 per cent, and, 
with the Hope water-motor fan, where the water-pressure 
is as much as 60 pounds to the square inch, the cost would 
not be more than one third of that of the one above cal- 
culated. 

It is also important to remember that, in this calcula- 
tion, enough power has been provided to remove the air 
independent of the aid of aspirating chimneys. The as- 
pirating chimney should be considered one of the essential 
parts of every school-house. It will cost nothing but the 
first cost of building, except in warm weather, when heat- 
ing is not necessary ; when, of course, means must be 
provided to build a fire in it for the sole purpose of cre- 
ating a draft. The aspirating chimney always serves a 



THE COST OF VENTILATION. 103 

good purpose, and, in ordinary conditions, will be suifi- 
cient for all the purposes of ventilation ; but there will 
be times when it will not be wholly adequate. In windy 
weather it is impossible so to regulate the draft that all 
the rooms of a large building will be ventilated equally. 

Again, it must not be forgotten that the aspirating 
chimney, drawing as it does the air from the room, is a 
vacuum-forming process, so that the incidental openings 
of doors and windows, as well as the crevices around im- 
perfect fitting ones, necessarily become inlets, thus inter- 
fering with the draft through the inlets intended to admit 
the fresh warm air. (Let it be repeated and emphasized 
here, that in cold climates double windows should be pro- 
vided. They lessen by one half the amount c^ heat lost 
by conduction through them, as well as shut off air- cur- 
rents where they are not wanted.) 

It becomes evident, then, that in systems now in use 
the plenum movement is necessary as a supplement to the 
aspirating chimney. This gives a fullness of air in the 
room, restoring the balance between internal and external 
air, made unequal by the aspirating chimney when acting 
alone. It also establishes the current independent of ac- 
cidental openings, and prevents interference to draft in 
windy weather. When thus working with the chimney, 
the power required is of course much less than when 
alone doing the whole work of moving the air. It should 
be under the control of a competent janitor, who could 
regulate its working to suit existing conditions. 

Considering, then, the plenum movement as a supple- 
mentary aid, taking advantage of modern improvements 
in propellers, and supposing the adjustments to be super- 
vised by one who understands the principles of ventila- 
tion, there remains no room for doubt as to whether this 
method of ventilation can be afforded. It not only can 



104: VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

be afforded, but it should be regarded as indispensable. 
Nothing is more needed in this age than a general en- 
lightenment on this subject of ventilation. Ignorance of 
employes should be no excuse for deferring necessary 
improvements. The improvements are needed by the 
public. The public are willing to pay for them, and 
there are persons competent to make them. When this 
kind of service is demanded, the supply will follow as 
a natural consequence. 



CHAPTER XVL 

WAEMIKG. 

Heat : The Amount needed for Comfort. — The degree 
of temperature most conducive to health is not a con- 
stant. The temperature varies not only for different in- 
dividuals but for the same individuals at different times. 
A youthful, healthy adult, actively employed, will be 
comfortable at a temperature of 60°, while elderly persons 
or invalids require a temperature of 68° to 75°. Children 
generally require a higher temperature than adults, and 
this especially when they are bodily inactive, as in the 
school-room. It is impossible to fix the temperature of a 
school-room to suit the changing conditions and indi- 
vidual characteristics of all, but some degree must be 
maintained which most nearly approximates the average 
necessities. A temperature of 70° is generally considered 
the proper degree for school-rooms ; it is probably as 
nearly correct as any fixed temperature can be. 

The relative humidity of the air has something to do 
with the temperature which will be most conducive to 



WARMING. 105 

comfort. In a moisfc atmosphere a temperature of 65° 
would probably seem as warm as 70° in a dry atmosphere. 
It is worthy of remark here that many medical authorities 
think that the American tendency is to overheat our 
houses, and that a much lower temperature than that 
generally maintained would be more healthy. Feeling is, 
no doubt, the truest guide to the proper temperature. 
The body should be made comfortable, even if a higher 
temperature be required than is thought normal. If an 
individual's circulation is so sluggish as to require a high 
temperature to maintain comfort, the remedy is not in 
an immediate deprivation of the heat, but in removing 
the desire for it by exercise and due attention to the laws 
of health. 

The Transmission of Heat.— Heat is transmitted in 
three ways — by conduction, by radiation, and by convec- 
tion. By conduction, heat passes through bodies from 
particle to particle, without any change of relative posi- 
tion between the particles. Heat applied to one end of a 
metallic rod passes through its entire length. The facility 
with which heat passes by conduction depends upon the 
nature of the medium through which it passes. All sub- 
stances conduct heat, but some so slowly that they are 
sometimes called non-conductors. In general, the metals 
are good conductors, while air, water, and dry vegetable 
fabrics, such as wood, cotton, etc., are bad conductors. 

The conductivity of bodies usually diminishes as the 
temperature is raised, though no definite laws of the rate 
of this decrease have been formulated. This fact becomes 
important in house-heating, and furnishes another objec- 
tion to overheating stoves and heaters ; for while in this 
condition they not only become pervious to poisonous 
gases, but by their diminished conductivity compel the 
heat to seek an exit through the chimney instead of con- 



106 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

ducting it into the room. In selecting stoves and heat- 
ers, due precaution should be exercised on these two im- 
portant points, thus securing a maximum of heat, and a 
minimum of escaping gases. Heaters should therefore 
be large, so as to furnish a large surface moderately- 
heated, instead of a small surface highly heated. They 
should be lined with fire-clay or brick, to intercept the 
poisonous carbonic oxide and other gases. By the con- 
ductivity of iron the heat stored up in steam or hot water 
is utilized in a room after having been carried some dis- 
tance from the source of the heat. It will also be a 
source of great waste if the convey-pipes leading to the 
several places where heat is wanted are not packed in 
some non-conducting material, to prevent the escape of 
heat into places where it is not wanted. 

Radiation. — Eadiant heat differs from conducted heat 
in several ways. While conducted heat requires a sensi- 
ble medium for its transmission, and a time which is de- 
termined by the nature of that medium, radiant heat re- 
quires no such medium, and travels with the velocity of 
light. Eadiant heat will perhaps be better understood by 
a few introductory remarks on light, with which radiant 
heat is probably identical. Without entering into a dis- 
cussion of radiant energy, it may be said that all experi- 
mental observation thus far serves to corroborate the 
theory that light is a mode of molecular motion in a sub- 
tile medium not cognizable to the senses and permeating 
all space. It travels at the rate of 18^,000 miles per sec- 
ond. Its effects on life are well known, it being the 
prime active agent in all vegetable and animal existence. 
If a beam of solar light be admitted into a darkened room 
and allowed to pass through a prism, it divides into seven 
parts, and, if projected on a white wall or screen, it will 
appear in as many different colors, red, orange, yellow. 



WARMING. 107 

green, blue, indigo, and yiolct, commonly called tlie solar 
spectrum. When passing from one medium to another 
of different density light is bent out of its direct course. 
This is termed refraction. Now, in the solar spectrum 
the several parts denoted by the seven colors are refracted 
at different angles, the red least and the violet most. It 
is this which makes the light spread out like a fan and 
appear as a continuous band on the screen. 

These colors, when examined separately, manifest 
properties somewhat different, though they have many 
l^roperties in common. The red ray — the least refracted 
— shows the greatest heat, and the violet the least. By 
Newton's interference disks it is proved that these rays 
also differ in wave-length, the red being the longest and 
the violet shortest, but their vibratory rapidity is in- 
versely as their length. In common, all these rays have 
the property of reflection, refraction, and polarization. 
The relevancy of these remarks will now appear. 

If the spectrum be examined, just beyond the red, 
where it appears dark, it will be found to possess the. same 
characteristics, except visibility, as other parts of the 
spectrum. The ratio of increasing heat from the violet 
to the red is continued into the dark part, which is found 
to be of a higher temperature than any other part. This 
part may be deflected from its course by a smooth surface, 
and collected by a lens, showing that it possesses in com- 
mon with light the properties of reflection and refraction. 
It differs from light only in being invisible. Its waves 
are longer and vibratory motion slower than the luminous 
parts of the spectrum. The waves and vibrations are not 
of the requisite length and frequency to affect the optic 
nerve. That is to say, there is nothing in the organ of 
sight to respond to waves and vibrations of this length 

and rate. 
11 



108 VENTILATION AND WARMING OF SCHOOL-BIJILDINGS. 

The effect of radiant heat from the sun, both lumi- 
nous and non-luminous, is well known to all. No arti- 
ficial heat can take the place of solar heat. The sanitary 
beneficence of sunshine is proyerbial. It is reasonable 
now to suppose that the form of artificial heat which 
most nearly resembles solar heat is most healthful. All 
bodies radiate heat. If two bodies are separated by noth- 
ing but air, each is constantly receiving heat from the 
other, but if one is of a higher temperature than the other 
the hotter body will radiate more than it receives, while 
the cooler body will radiate less than it receives ; hence, 
by this process of exchange, the heat of the two bodies 
will become equalized. The air between the bodies will 
not be affected by the radiant heat of either, and this is 
equally true whether the radiant heat is luminous, as 
from an open fireplace, or non-luminous, as from stoves 
or heated pipes. 

Eadiant heat is transmitted in straight lines, and, like 
light, diminishes in intensity as the square of the distance 
from the source of heat increases. It passes through the 
air without affecting it, but heats all solid bodies upon 
which it strikes. Tyndall, by a series of experiments, has 
concluded that vapor of water in the atmosphere, if in 
considerable quantity, intercepts the passage of radiant 
heat, and to such a degree as almost to make a humid air 
opaque to radiant heat. This, however, has not been 
verified by other experiments. 

The air of a room heated by radiation can not be ac- 
curately tested by a thermometer, as the bulb receives 
radiant heat, while the air surrounding it remains cool. 
To prevent this, the bulb should be surrounded by a 
bright piece of tin, to reflect away the radiant heat. 

One advantage of radiant heat is that it warms the 
body and the objects in the room without hpating the air 



WARMING. 



109 



we breathe. An accompanying disadvantage is that, in 
ordinary heating by radiation, especially that of the fire- 
place, the radiant heat can warm but one side of the body 
at the same time. There is no doubt that if the body 
could receive sufficient radiant heat to warm it on all 
sides an atmospheric temperature of 50° would be more 
healthful than a higher one. 

Radiant heat is believed to possess peculiar sanitary 
virtues, and we have seen good reasons for this belief. 
Some writers even express the relative values of con- 
ducted, radiant, and convected heat by characterizing 
radiant heat as "golden," conducted heat as "silver," 
and convected heat as " copper." From the earliest 
times the open fire has been instinctively felt to possess 
special virtue. . The peculiar exciting glow produced by 
the fireplace is the common experience of everybody. Its 
peculiar virtue is not alone in abstracting foul air from 
the room, but in the nervous stimulus of direct radial 
contact. 

The relative value of luminous and non-luminous ra- 
diation is not known, but there is little doubt that the 
former far exceeds the latter. There is reason for this. 
The luminous heat appeals to one more sense, that of 
sight, and, even though the physical qualities of the two 
kinds were otherwise the same, this alone might materially 
modify the total effect. We always look at the glowing 
grate, and are never indifferent to it. The direct lumi- 
nous radiation of a fireplace is the best substitute for sun- 
shine, and the direct radiation of a heated body is proba- 
bly next in value. It will be seen, however, in our dis- 
cussion of combined methods of heating and ventilating, 
that direct radiation alone is not sufficient. 

Convection. — In fluids, such as air and water, the 
composing particles are free to move among one another. 



110 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

there being no friction or cohesion between them. When 
any of these particles become heated by contact with a 
hot body they expand, decrease in density, and rise, other 
particles moving in to fill their places. The circulation 
thus caused is termed convection. Convection is not, 
like radiation, a specific kind of heat, but is simply a 
mode of heat-conveyance. The particles, when separately 
considered, are heated by conduction, when they at once, 
by their diminished specific gravity, rise and give place 
to others to be heated in the same manner. The process 
may be likened to a large number of pupils crowded 
around a stove ; the nearer ones become warm, fall back 
and give place to the others, till the whole number be- 
come warmed. It is by convection that air and water are 
heated. Both of these fluids are poor conductors, and 
were it not for the lack of cohesion between their parti- 
cles there would be no hope of warming them. Their 
non-conducting property may be proved by trying to heat 
them from the top downward. If ether be poured on the 
surface of water it may be burned off without affecting 
the bulb of a thermometer placed half an inch below the 
surface of the water ; but the same amount of heat ap- 
plied at the bottom of the containing vessel would sensi- 
bly raise the temperature of the whole contents. It is 
evident, then, that air or water must be heated at the 
bottom. 

To prevent the too rapid escape of heat, warm air is 
sometimes admitted at the top of the room, and drawn 
out at the bottom near the floor. This has been tried in 
some of the European hospitals. As naturally to be ex- 
pected, this method has not been successful. It is work- 
ing against the force of gravity instead of with it. If 
accomplished at all, it must be at the expense of con- 
siderable power. Hot water can by means of a syringe 



METHODS OF WARMING. HI 

be forced to the bottom of a vessel of cold water, thus 
warming it, but it takes power to do it. The same prin- 
ciple holds when dealing with air. 



CHAPTEE XVII. 

METHODS OF WAKMIKO. 

The various methods of warming school-houses will 
be considered in connection with their accompanying pos- 
sibilities of ventilation ; for a system of heating the air 
which does not at the same time provide for its necessary 
renewal is hardly worthy of consideration ; Such meth- 
ods, therefore, will be considered only to expose their 
defects, that they may the sooner give place to better ones. 

The Open Fireplace. — The open fire, as a means of 
heating, is coming to be regarded as an antiquated insti- 
tution, which very well answered the purpose of our un- 
learned forefathers, but which is now regarded as too 
primitive for this age of steam, hot air, and patent stoves. 
While the open fire still has a limited existence in private 
dwellings, in the form of ornamental, badly-constructed 
grates, and dummy mantels, it is no longer even thought 
of in this country as a means of warming school-houses. 
It will receive attention here, not as an historical relic, 
but partly because it is the best arrangement, as far as it 
goes, for the combined purpose of warming and ventilat- 
ing that has ever been devised, and partly because the 
best school-house in the world — the City of London High 
School — is so warmed, ventilated, and made comfortable. 

The history of the open fireplace, from its first use by 
the Eomans, need not here be given ; we are interested 



112 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

only in that form of it which best conforms to the prin- 
ciples of heating and ventilating. One of the best con- 

FiG. 16. 




structed fireplaces is Dr. Arnott's smokeless grate, which 
may be understood by reference to Fig. 16. The chim- 
ney, Tsuio, is of the usual construction ; al ef repre- 



METHODS OF WARMING. 113 

sent the front bars of a bottomless grate, it being open 
for the admission of coal, and needs to be supplied only 
once a day. The fire is lighted by laying on the surface of 
the coal, at ef, a sufficient quantity of light wood to insure 
ignition. The coal below becomes heated ; the bitumen 
rises and burns. As the fire burns low, it is raised by 
means of a lever, h, working in the notched bar Z, which 
pushes up a false bottom s s, upon which the coal rests. 
The fire is supported by air which passes through the 
bars in front ; v represents a yalve or damper in the wall 
near the ceiling, and regulates an opening into the chim- 
ney. This further serves as a ventilator, and may be con- 
trolled by means of the cord x suspended within easy 
reach. In ordinary fireplaces the large space above the 
fire robs the room of much of its pure air, wTiich mixes 
with the smoke in large quantities and passes up the 
chimney. This is prevented in the grate now under con- 
sideration by a device, here described in Dr. Arnott's own 
words : *^ The whole of the. air so contaminated, and 
which may be in volume twenty, fifty, or even a hundred 
times greater than that of the true smoke or burned air, 
is then all called smoke, and must all be allowed to as- 
cend away from the room, that none of the true smoke 
may remain. It is evident, then, that if a cover or hood 
of metal be placed over a fire, as represented by T in the 
diagram, or if, which is better, the space over the fire bo 
equally contracted by brickwork, so as to prevent the 
diffusion of the true smoke or the entrance of pure air 
from around to mix with it, except just what is necessary 
to burn the inflammable gases which arise with the true 
smoke, there will be a great economy. This is done in 
the new fireplace, with a saving of from one third to 
one half of the fuel required to maintain a desired tem- 
perature. In a room the three dimensions of which are 



114 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

15 feet, 13i feet, and 12 feet, with two large windows, 
the coal burned to maintain a temperature of 65° in cold 
winter days has been 18 pounds for 19 hours, or less than 
a pound an hour." 

The room here supposed has about one fourth the ca- 
pacity of an ordinary school-room. This fireplace would 
then, according to Dr. Arnott, warm a school-room with 
less than 4 pounds of coal per hour. But we found by a 
previous calculation that about 18 pounds are necessary 
when the conditions of ventilation are all provided for 
and the temperature to be raised is 35°. It would appear 
from this great difference that, after making due allow- 
ance for the four extra windows and for the rigor of our 
climate over that of England, a form of open fire, such 
as that just described, is as economical as other modes of 
heating. 

Heat is further economized in Boyd's open fireplace, 
by means of which, in addition to Dr. Arnott's plan, the 
cold fresh air is admitted from the outside to a chamber- 
box just back of the fire. This being put in communica- 
tion with the room furnishes an inlet of pure warm air. 
It is this kind of fireplace which is used in the magnifi- 
cent high-school building of London, which has only 
recently been finished. Further provision was made in 
the construction of this school-house in making foul-air 
openings near the ceiling and leading to a mammoth as- 
pirating chimney extending to the basement. For the 
open fireplaces a separate flue is provided for each room 
independent of all the others. 

In a climate in which the heat thns supplied is suffi- 
cient, this plan is about as nearly ideally perfect as can be 
imagined. Here the room is heated by convection of the 
ascending warm currents rising from the fire, by that 
which comes in from behind the grate, and, best of all. 



METHODS OF WARMING. 115 

by the direct radiation of live luminous lieat direct from 
the open fire. The fresh air is warmed before entering, 
without being overheated. The room is ventilated both 
from the top and from the bottom of the room. The 
COg, and other respired impurities, always at the top 
of the room, are drawn off by the aspirating chimney. 
Other foul colder gases, from the floors and neighboring 
closets, which may be lurking in the lower strata of the 
air, are effectually drawn off by the draft of the fireplace. 

Whether this mode of warming would be adequate for 
the coldest days of an American winter is not known. It 
has never been tried. But it is safe to presume that it 
would be sufficient for nine tenths of the time in which a 
fire is needed. In severe weather it could fee supple- 
mented with steam-pipes, of which more hereafter. 

Stoves. — Everybody who reads this book knows what 
a stove is, hence no general definition need be given. As 
a means of warming, a stove may be good or bad, according 
as the principles which should govern warming and ven- 
tilation are conformed to or violated. As the latter prac- 
tice is more common, stoves are growing into general dis- 
favor. 

The necessary conditions governing the selection of a 
stove are : 1. It must be large, having sufficient surface 
to warm sufficiently without overheating. The evils of 
overheating the air have already been referred to in 
another place, and it may be here emphasized that air 
coming in contact with a highly-heated surface is ruined 
for purposes of respiration. The peculiarly disagreeable 
odor of such air is probably due to a charring of the or- 
ganic matter contained in the air. The relative humidity 
of such air is so low that it is rendered not only unfit for 
respiration but ruinous to all animal tissue with which it 
comes in contact. 2. A stove should be lined with fire- 



116 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

brick, or other similar material, to intercept poisonous 
gases whicli would otherwise pass through the heated 
iron into the room and contaminate the air. 3. It should 
combine or be accompanied with some eflBcient means 
of ventilation. 4. The smoke-pipe should be long, taking 
a turn around the room so as to economize the heat. 

These requirements being complied with, there is lit- 
tle objection to the use of stoves. On the contrary, there 
is much in favor of them. In point of economy it is 
the cheapest means of warming known. But where the 
requirements just enumerated are not observed — when 
stoves are small, without lining, often heated to redness, 
and without means of ventilation — they are not only use- 
less but become engines of destruction. Hundreds of 
different kinds of stoves are in use, but I shall specify 
no further than is necessary to illustrate the correct ap- 
plication of underlying principles. After canvassing the 
whole ground, I return to Dr. Arnott, who understood 
principles, and knew how to apply them. Fig. 17 illus- 
trates the Arnott closed stove, and is thus described by 
him : " The complete self-regulating stove may indeed 
be considered as a close stove with an external case, and 
certain additions and modifications to be described. The 
dotted lines and the small letters mark the internal stove, 
and the entire lines the external case or covering. The 
letters A B C D mark the external case, which prevents 
the intense heat of the inner stove, ahcd, from damaging 
the air of the room. F is the regulating valve for ad- 
mitting the air to feed the fire (see Fig. 4). It may be 
placed near the ashpit-door, or wherever more convenient. 
The letters // mark the fire-brick lining of the fire-box 
or grate, which prevents such cooling of the ignited mass 
as might interfere with steady combustion. H is a hop- 
per or receptacle with open mouth below, suspended above 



METHODS OF WARMING. 



117 



the fire like a bell, to hold a sufficient charge of coal for 
twenty-four hours or more, which coal always falls down 



Fig. 17. 




of itself, as that below it in the fire-box is consumed. The 
hopper may at any time be filled with coal from above 
through the lid K, of the hopper, and the other lid K' of 
the outer case. These lids are rendered nearly air-tight 
by sand- joints ; that is, by their outer edges or circumfer- 
ence being turned down and made to dip into grooves filled 
with sand at e e. The burned air or smoke from the fire 



118 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

rises up in the space between the hopper and the inner 
stove-case, to pass away by the internal flue x into the 
other flue X of the outer case. L is the ash-pit under the 
fire-bars ; G- is the ash-pit door, which must be carefully 
fitted to shut in an air-tight manner by grinding its face 
or otherwise. The coal is intensely ignited below where 
the fresh air maintains combustion, but colder gradually 
as it is further up. Only the coal in the fire-grate below, 
where the fresh air has access to it through the fire-bars, 
can be in a state of active combustion." 

This, it will be observed, is the origin of the modern 
" base-burner," which is a somewhat degenerated modifi- 
cation. Modern stove-mongers study for ornament rather 
than utility. 

To be complete as a ventilator, furnishing an abun- 
dance of pure warmed air, the space between the inner 
and outer stove-cases should be in connection with the 
outside air by means of an air-duct, in which there would 
be found an inflowing current as the air rises in becoming 
heated. The outer flue X should be open into the room 
in order that this warmed air may be utilized. This was 
not the intent of Dr. Arnott, as he supposed the air in 
contact with the inner case to be vitiated by excessive 
heating. But the stove could easily be made of such a 
proportion between the size of the coal-hopper and the 
weight and surface of iron used in the construction of 
the cases as, together with the cold-air connection, to pre- 
vent overheating. 

A very simple, effective, and inexpensive stove is il- 
lustrated by Fig. 18. F represents a stove of ordinary 
construction, upon which is placed a large double drum, 
the outer part, F, of which is in connection with the fire, 
and conducts away the smoke and waste products through 
the pipe P. The inside drum A communicates with the 



METHODS OF WARMING. 



119 



outside air by the duct D. The size of the drum and the 
length of the pipe P should be such as to utilize all the 



Fig. 18. 





heat before the chimney is reached. The action is sim- 
ple. As the air inside the drum becomes heated by the 
fire-draft around it, it expands, rises, and passes out at B 
12 



120 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

into the room. The partial vacuum thus formed is filled 
with inflowing cold air through the duct D. If desired, 
an upper room may be heated by the same fire by extend- 
ing the pipe P through the ceiling, enlarging it in the 
room above into a drum of the same construction as the 
one described. A patent was granted in 1884 to A. M. 
Hicks and A. Dishman, of Kentucky, for the invention 
of a stove of similar construction. 

Stoves, while not the best means of warming, may by 
a little care and attention be made serviceable and eco- 
nomical. Considering their comparative simplicity and 
easy adjustment, and the qualifications of the average 
builder, it is questionable whether it would not in the 
majority of cases be better to make use of improved stove 
heating than tamper with those more improved systems, 
the adjustment and management of which , require scien- 
tific knowledge and technical skill. A fairly good system 
properly managed is better than a more excellent one in 
unskillful hands. 

Many forms of open stoves have recently been made, 
intended to combine the advantages of the closed stove 
and the open fireplace ; among which may be mentioned 
the so-called '^ Baltimore Heater." It consists of an open- 
front stove set back into a chimney recess resembling the 
common fireplace. The smoke-pipe extends up through 
the entire length of the chimney, leaving the space be- 
tween it and the inside walls of the chimney as a venti- 
lating flue which may be put in communication with the 
room. 

The Ruttan System. — Stoves may be greatly enlarged 
and placed in a separate apartment, preferably a basement, 
where they are made to furnish the heat to the various 
parts of a building by means of communicating tubes. 
They are, when so situated, sometimes called furnaces. 



METHODS OF WARMING. 121 

Many different kinds of furnaces are in use for thus sup- 
plying rooms with hot air, all having for their object the 
heating of air and transferring it to the various rooms. 
Many of these furnaces are constructed with the sole 
object of heating, no provision being made for ventila- 
tion. Some of these fulfill their object well, but, as it is 
not the purpose here to consider the merits of heaters 
simply as such, they will not be discussed. 

The most which has been accomplished in the way of 
warming by means of hot air, where ventilation at the 
same time has not been ignored, has been done by the 
so-called Ruttan system. This system of heating and 
ventilating is coming into quite extensive use in Canada 
and many of the Northern States, where it is receiving 
many testimonials of approval. 

For some of the excellent features which this system 
undoubtedly possesses, and for some of the overdrawn esti- 
mates of its merits made by its friends, its merits and 
demerits will here be considered. The system combines 
the patented inventions of Henry Ruttan, of Canada ; J. 
D. Smead, of Toledo, Ohio ; and B. R. Hawley. For 
heating, the tubular furnace is used, which, on account 
of the large surface which is thus brought in direct con- 
tact with the fire, is economical as a consumer, and the 
large surface which is also subjected to the air makes it 
effective as a heater. It conforms well to the require- 
ments of a heater which have already been insisted on 
under the discussion of stoves. The fire-box, by its con- 
struction, presents a large surface to the fire and to the 
air. The surface is further increased by causing the 
smoke and burned products to pass successively through 
the tubes. The furnace is set into masonry, into which 
the cold air is admitted for warming, and passes out at 
the tubes to the rooms. The method of admitting the 
6 



122 VENTILATION AND WARMING OF SCIIOOL-BUILDINGS. 



heated air into the room is embodied in an invention of 
Mr. Smead, patented by him in 1882. It may be under- 
stood by reference to Fig. 19, which represents a vertical 



Fig. 19. 




transverse section through the heater and lower part of 
one of the flues. A represents the building, B the air- 
flue, C the heating chamber, D the cold-air duct, E the 



METHODS OF WARMING. 123 

furnace chamber, F a wall separating the furnace from the 
flues, Q an opening from the furnace into the flue, II the 
opening from cold-air duct into the flue, I a hinged valve 
for regulating the relative supply of hot and cold air, J 
the opening into the room to be warmed, L a hand-knob 
for raising and lowering the valve I, d sl weight to hold 
the valve in position. The arrows show the direction of 
the air. The action of this arrangement is as follows : 
The air in the chamber becomes heated, rises and passes 
up the flue M, and into the room through J. The cold 
air flows in at D to fill the partial vacuum thus made. 
When the room becomes too warm, the inflowing hot air 
is mixed with cold air by turning the knob L, which 
raises the valve I, closing the hot-air passage G and open- 
ing the cold-air passage B. The height to whicn this valve 
is raised regulates the relative size of the hot- and cold- 
air openings. It will be well at this point to notice that, 
while the relative size of the hot- and cold-air openings 
may be thus regulated, it is doubtful whether the same 
proportions maintain between the hot and cold air pass- 
ing through them. The quantity of inflowing hot air 
may undoubtedly be regulated by this valve, by ojiening 
and closing it ; but how the cold air is to rise and flow in 
its place is not so clear. Suppose the valve be raised so 
as to make the size of the hot- and cold -air openings 
equal, what will then be the action ? The hot air rising 
through the flue has a vacuum-forming tendency, and it 
is supposed by the inventor that the cold air at the bottom 
of the flue will rise up to fill the partial vacuum. This it 
might do were there not a source of supply by which the 
vacuum is supplied with less resistance. There is an in- 
exhaustible supply of hot air coming from the furnace, 
already possessing a tendency to rise, and half closing the 
hot-air opening, as in the case supposed, further increases 



124 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

the tension of the hot air thus resisted as it rises from the 
furnace. Will not, then, this supply of hot air with high 
tension be sufficient to supply all yacuum which the air 
rising in the flue will create ? If the cold air will rise 
under these conditions, it is difficult to see why the cold 
air of the room into which the warm air enters will not 
rise along with and be drawn up by it as it passes in at J 
and rises to the toj) of the room. 

This is not a case parallel with the aspirating chim- 
ney, where hot air rising in a shaft will cause cooler air 
to flow in through openings into it. In this case the 
partial yacuum has no other adequate source of supply, 
which we haye seen is not the case in the flue under 
consideration. 

It is not here maintained, however, that this yalye is 
useless ; on the contrary, it may be, under certain con- 
ditions, yery useful. If it be nearly or quite raised, so as 
to shut off most or all of the hot air, and if there is a 
good aspirating chimney drawing the foul air from the 
room which is being supplied, and if the doors and win- 
dows are carefully closed, then the cold air will rise in 
this cold-air duct. But it is safe to conclude that all 
these conditions are necessary. If there is no aspi- 
rating chimney there will be no vacuum-forming tendency 
in the room sufficient to cause cold air to rise. If a door 
or window is opened, the draft in all cold-air ducts imme- 
diately ceases, as air, like all other moving bodies, seeking 
the line of least resistance, will come from a source where 
it is least opposed ; and through an open door or window 
the resistance by friction is nothing, while in the cold-air 
flue it is considerable. Here, let it be observed, is another 
argument for double windows and spring-closing doors. 

In the Ruttan system the foul air is drawn out of the 
room from the bottom through registers near the floor. 



METHODS OF WARMING. 125 

These outlets are placed, when convenient, on the sides 
of the room opposite the final outlet, so that foul warm 
air, as it leaves the room, will pass under the floor which 
it is thus intended to warm. The foul air thus passing 
from the different rooms is all collected into a foul-air 
room adjacent to the smoke-chimney, into the bottom 
of which it communicates by a large opening. 

The theory of the system may be summarized as fol- 
lows : The air warmed by the furnace rises through the 
air-flue into the room, where, within convenient reach, a 
hand-knob is placed for regulation of hot and cold air. 
The warm air, after its admission, rises to the top of the 
room which, on being filled from the top downward, 
presses the cold air down aud out of the oujjets. The 
foul air, it is claimed, being ^^ at the bottom," is thus 
drawn off, and the upper part of the room kept constantly 
filled with pure warm air. The floor is warmed by the 
foul air as it passes beneath on its way out. This foul air 
is kept in motion by the draft of the chimney into which 
the foul-air room opens. It may be said in favor of this 
system that it shows throughout a studied effort toward 
conformity to physical laws, and is therefore a valuable 
contribution toward the solution of the difficult and all- 
important problem of ventilation. It is an ingenious 
system, and is doing comparatively good service. The 
critical review to which it will now be submitted is in- 
tended to be in the interest of truth and the public good, 
and toward suggesting improvements rather than con- 
demning the system. 

In the first place, considering the large amount of 
friction which the air necessarily encounters in finding 
its way out, and the rapid passage of air which is neces- 
sary to secure proper ventilation, a higher degree of fur- 
nace heat is necessary than is harmless to the air. 



126 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

Again, if the air entered the room at the temperature 
of comfort, as claimed in the theory, it would be too cold 
to be endured after having made its circuit to the top of 
the room and settled down to the point of utilization. 

These two reasons make the overheating of the air 
unavoidable. We have seen that overheated air is dam- 
aged for purposes of respiration ; and it is evident that 
the heat necessary to raise air to a high temperature is 
nearly all lost, as this surplus heat must pass away through 
walls and windows in cooling down to the degree of com- 
fort. 

The origin of this difficulty seems to be in the lack of 
proper distribution of the air as it enters the room. When 
the incoming air is all at one place, it will of course rise 
to the top of the room before it becomes sufficiently 
vitiated to allow its escape before it has been used. It 
must therefore be retained, but it can not be retained 
without placing the outlets below. If the air was prop- 
erly distributed as it enters, it would be sufficiently viti- 
ated to be allowed to pass out at the top of the room, on 
reaching that point, the natural place for its exit. 

The placing of the outlets below is further justified, 
by the theory of this system, in supposing the vitiated air 
is at the bottom of the room. The fallacy of this assump- 
tion is shown in another place, under the consideration of 
the position of outlets, and need not be repeated here. 

A condition of things may exist, and probably does in 
this system, where the most of the uudiffused CO2 occu- 
pies a position somewhat near the breathing line. If the 
incoming air is warmer than the breath — about 95° — it 
will rise above the breath and prevent its ascent higher 
than that stratum of air having a temperature of 95°. In- 
stead, therefore, of making a dive for the floor, the re- 
spired breath, carrying CO3 and organic matter, will rise 



METHODS OF WARMING. 127 

a short distance, and, before passing out of the room, 
must again cross the breathing line. Kow, the shorter 
the distance between this stratum and the breathing line, 
the less opportunity for diffusion to take place in time to 
prevent rebreathing the expired impurities. 

An objection to the arrangement for warming the floor 
might reasonably be urged in the fact that so large a part 
of the building is submitted to the contamination of foul 
air with no provision for cleansing. The walls of a shaft 
or room in which there exist large quantities of air viti- 
ated by respiration soon become coated with an offensive 
and poisonous accumulation of organic matter which, if 
not removed, is liable to contaminate the entire building, 
and in case of temporary reversal of the draft, #s is some- 
times sure to take place in warm weather, when little or 
no fire is required, the air, in passing over this foul mat- 
ter, becomes unfit for respiration before it reaches the 
room. All foul-air passages should be accessible to the 
brush of the janitor. 

One obstacle in the way of this system is the difficulty 
of managing the average builder. In order that the pos- 
sibilities of the system may be realized, buildings must 
be constructed from the beginning with special design for 
its application. In buildings not specially constructed 
for this system it is practically worthless, and the same 
is true in buildings improperly designed for it by design- 
ers who do not fully understand the principles which the 
system requires of them to materialize. This is in itself 
no fault of the system, but is, in the present state of me- 
chanical service, an inevitable obstacle. 

It is not unfrequent to see school-houses built for this 
system where the construction ignores the very principles 
upon which the success of the system mainly depends. 
In one instance which I now have in mind, and which I 



128 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

had excellent opportunities of observing, the foul-air out- 
lets led to single chimneys for each room, which were 
closed up solid at the bottom, and unconnected with the 
smoke-chinme}" or other source of heat. The windows 
were numerous and loosely fitted, which allowed the hot 
air to pass out at the top of them before it arrived at a 
point low enough to be utilized. The small dummy aspi- 
rating chimneys, having little draft, failed in their legiti- 
mate function of removing the foul air of the room 
in order to give place to the incoming hot air, which 
could not otherwise find an entrance sufficient to warm 
the room. These circumstances admitted of but one 
result. The hot air, all that oould be forced to enter, 
found a lodgment in the upper part of the rooms, where 
a temperature of about 200° was maintained, while at the 
floor it was little above the freezing point. Of course the 
apparatus had to be tai^en out. 

In conclusion, it may be said of the Euttan system 
that, if the requirements of the theory be carefully con- 
formed to in the construction of the buildings, the win- 
dows and doors made tight-fitting and kept closed, it 
will work comparatively well, yet even at its best it has 
inherent defects which must be recognized and met be- 
fore it can be received as a perfect system. 



STEAM HEATING. 129 

CHAPTER XVIII. 

STEAM HEATIKG. 

Ik heating with steam, water is converted into steam 
in a boiler heated by a furnace situated in the basement 
or other conyenient locality. The steam is then conveyed 
by means of pipes to the parts of the building to be 
warmed. 

It will be seen by a careful reading of the foregoing 
pages that one of the chief defects in all systems of warm- 
ing and ventilating so far considered is the inadequate 
distribution of the warmed air. This is a matter of prime 
importance. Heat should be furnished not oi|Jy of the 
necessary amount, but it should be furnished in such a 
manner that it can be utilized. 

We have seen that it is impossible thoroughly to do 
this by stoves and hot-air furnaces in buildings more 
than one story in height. If our school-houses could be 
confined to a single story, furnace-warmed air might be 
used, and perfect ventilation be attained. The English 
House of Commons is heated by means of furnace-warmed 
air, on a modified plan of Dr. Reid, and all the required 
conditions of ventilation and distribution are there com- 
plied with. But the same results would not be possible 
in an upper story of a building. 

In this building a hot-air chamber, extending beneath 
the entire floor, supplies the room with warmed air ad- 
mitted through a perforated floor. Ventilation is at the 
top, and the foul-air flues have their opening into an as- 
pirating chimney. 

In buildings of several stories, containing many rooms, 
the difficulties of heat distribution without waste are met 
by the use of steam. This is inevitable from the natural 



130 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

properties which steam possesses. A correct popular un- 
derstanding of these properties would eventually settle 
the question as to the best method of warming large 
school-buildings. While these properties are easy of dem- 
onstration, it is curious what erroneous notions are cur- 
rent concerning them. 

Of course it can not be expected that the printed ad- 
vertisements prepared by furnace-heating companies will 
contain much that is scientifically reliable concerning the 
peculiar heating advantages of steam ; and while it might 
be pertinent to ask why they do not remain silent regard- 
ing that which they either misrepresent or misunder- 
stand, it may perhaps be excused as a sort of special 
pleading which has come to be regarded as legitimate in 
advertising. 

But this is not the only source of published error con- 
cerning the properties of steam. A single instance will 
suffice. W. 0. Whitford, ex-Superintendent of Public 
instruction of Wisconsin, in a book on '^ Plans and Speci- 
fications of School-Houses," in referring to steam heat- 
ing says : '^ A very considerable percentage of the force 
derived from the heat applied to the water in generating 
steam is lost in expanding and driving this steam along 
the iron pipes or through the radiators. In other words, 
the heat of the burning fuel appears in part in mechani- 
cal action and not in temperature." 

That this mechanical action is lost is a somewhat 
strange doctrine. A few quotations from authors who 
have given sjoecial attention to physical laws will be suffi- 
cient to stand against this view. 

Gage, in his '^ Physics," says : ''Heat that is con- 
sumed in liquefying solids and vaporizing liquids is 
always restored when the reverse change tahes place, . . . 
The fact that steam in condensing generates a large 



STEAM HEATING. 131 

amount of heat is turned to practical use in heating 
buildings by steam." 

William J. Baldwin, a scientific mechanicar engineer, 
in his work on ^^ Steam Heating for Buildings," says : 
'' When a solid becomes a liquid, or a liquid becomes a 
vapor^ heat is absorbed more than was necessary to raise 
it to the temperature of conversion, and this latent heat 
does work in the destruction in the force of cohesion and 
other occult changes which take place, and must be ab- 
sorbed /rom so?ne other substance. In the case of steam 
in a boiler, it comes from the fuel during combustion, 
and when a pool of water is vaporized in the street, it 
comes from the sun directly, and from the earth, air, etc., 
indirectly. When steam or vapor is condensed this same 
quantity of heat that was received, no matter where, is 
given off to any substance within its influence, air, water, 
etc., colder than itself, and it is this property, to convey 
more heat within ordinary controllable temperatures than 
any other substance, which makes water and its vapor so 
valuable." 

These properties of steam may be demonstrated by a 
simple and interesting experiment : 

An apparatus, consisting of a flask, lamp or Bunsen 

burner, bent tube, and beaker, is arranged as shown in 

Fig. 20. Into the flask A pour one ounce of water at 

32° Fahr., and into the beaker C pour 5 J ounces at the 

same temperature. In a short time the water in A will 

be converted into steam, which will pass through the tube 

B and be condensed in the beaker C. Immediately after 

the total evaporation of the water in A, the water in C 

will be found by testing to be at a temperature of 212° 

Fahr. By carefully noting the time which elapsed from 

the first application of the heat till boiling commenced, 

and also from when boiling commenced till the eyapora- 
13 



132 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

tion was completed, it will be found that the latter time 
is 5J times the former, that it requires 5J times as long 



Fig. 20. 




to conyert boiling water into steam as it does to raise 
water from the freezing to the boiling point.* 

Now, these facts teach, first, that, as the application of 
the heat is constant, 5^ times as much of it exists as la- 
tent heat than exists as sensible heat. During the entire 
process, neither the boiling water nor the steam acquires 
^ temperature above 212°, the boiling-point of water. 
Second, that this so-called latent heat is really no heat 
Ski all, but mechanical energy, into which the sensible 

^ To avoid accident in this experiment, the flask should not be al- 
lowed to boil quite dry^ ^s this would cause a vacuum to be formed in 
the flask, which would suddenly be filled by a rush of water from the 
beaker through the tube, fo avoid a similar result, the tube should 
always be raised out of the beaker before the heat is removed, for if the 
water ceases to boil the steam will cease to be driven off, and a vaccuum 
will result the same as though the fl^sk: were allowed to boil dry. 



STEAM HEATING. I33 

heat of the flame was converted ; this energy being suffi- 
cient to overcome the cohesion between the particles of 
the water and to transfer them against gravity over into 
the beaker. Third, that as the water in the beaker, con- 
taining 5J times as much as was evaporated, was raised 
to a temperature equal to the highest temperature of the 
steam, this latent heat, in the form of mechanical energy, 
appears as sensible heat as soon as condensation takes 
place. Fourth, that during the passage of the steam 
through the tube, none of the latent heat is lost ; that 
its re-appearance as sensible heat is reserved until the in- 
stant of condensation. 

In view of these principles, practical insight need not 
be very far-reaching to see the great advantage possessed 
by steam for the purposes of heating, when heat is to be 
carried to some distance and distributed. The mechani- 
cal work necessary to "drive steam through pipes and 
radiators " exists in the steam itself, for its inherent j^rop- 
erty of expansion makes it self-driving. 

If steam-pipes could be perfectly insulated, so as ab- 
solutely to prevent exchange of temperature between them 
and the air, heat could be transferred to any distance 
whatever, and without loss. Perfect insulation is of course 
impossible, but it may easily be made sufficiently good to 
render the loss in a single large building practically 
nothing. 

This has been demonstrated by Mr. Holly, who has 
extended the system from heating a few buildings to as 
many hundreds, where the steam is all generated iu one 
place and conveyed through carefully insulated tubes to 
the several houses. 

The method of insulating the pipes which Mr. Holly 
used maybe described in the words of his circular : *'The 
pipe is i^laced in a lathe, and wound about first with as- 



134 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

bestos, followed by hair felting, porous paper, manilla 
paper, finally thin strips of wood laid on lengthwise, and 
the whole fastened together by a copper wire wound spi- 
rally over all. This is thrust into a wooden log, bored to 
leave an intervening air-chamber between the pipe and 
the wood, and of sufficient size to leave from three to five 
inches of wood covering. The elasticity of the wrappings 
permits the free expansion and contraction of the pipe 
irrespective of the wooden log, which is securely anchored 
and made immovable. The whole is placed in a trench a 
short distance below the surface without regard to frost. 
At the bottom of the trench is laid an earthen tile drain 
to carry off any earth moisture, and in order further to 
insure the continuous dryness of the wooden log inclosing 
the pipe." 

Such careful insulation is of course wholly unnecessary 
in the heating of a single building. This description is 
given simply as an example in further demonstration of 
the principles in steam heating. 

Mr. Holly also demonstrated, by a carefully conducted 
experiment, that steam may be conveyed through 1,600 
feet of three-inch pipe, with a loss by radiation of only 
2J per cent. This is sufficient to show that in single 
buildings, where the risers are about the only pipes from 
which radiation is not wanted, the loss may be regarded 
as practically nothing. 

It has already been noticed that steam, when not un- 
der pressure, has a temperature of only 212°, that of boil- 
ing water. When, however, its free expansion is arrested, 
its temperature will increase in proportion to the pressure 
to which it is subjected. It is better, therefore, in order 
not to overheat the air by contact with superheated iron, 
to have the pressure as light as possible. Here is another 
important advantage of steam heating : the air need never 



STEAM HEATING. I35 

be overheated if a proper regulation of pressure be ob- 
served, and a sufficient amount of piping be used to fur- 
nish the requisite surface for radiation. 

Steam-pipes can be carried to any place in a building 
where heat is desired. In most other systems of heating 
the heads of the occupants of a room inevitably occupy 
a position having a higher temperature than that of the 
fept. This is exactly the reverse of what it should be. 
Nothing is more subversive of good circulation than cold 
feet. On the other hand, if the feet are kept warm, good 
circulation may comfortably be maintained, even when 
other parts of the body are subjected to a comparatively 
low temperature. 

An arrangement of steam-pipes beneath the floor, as 
hereafter described, would settle the question of cold feet, 
and remove the necessity of so high a temperature in 
other parts of the room as is commonly maintained. 
There remains no question, then, as to the superior fa- 
cilities of steam for heat distribution. 

Its cost may be figured otherwise than from the above 
negative consideration of the loss. The latent heat of 
steam is 960, that is, it requires 960 units of heat to con- 
vert one pound of boiling water into steam. This is 
really the amount that is actually realized as heat. The 
hot water, when first condensed in the pipes, does on its 
return impart some of its heat to the room, but the same 
amount will be necessary to raise it again to the boiling- 
point in the boiler before it can again be utilized. Theo- 
retically, one pound of coal will furnish heat sufficient to 
convert 14 pounds of water into steam, but in the average 
practice only 9 pounds are realized. Then 960 X 9 = 
8,640 is the number of thermal units which can be real- 
ized from one pound of coal. 

It was found, when calculating the cost of heating in 



136 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

another place, that 142,959 units of heat are necessary to 
supply the requirements of one average school-room for 
one hour, where all the demands of warming and yenti- 
lating are rigidly complied with. Now, 142,959 -r- 8,640 
= 16 "66, the number of pounds of coal necessary to sup- 
ply one room for one hour. In the former calculation it 
was found that 18'3 pounds was the number required, 
which shows nearly 2 pounds per hour in favor of steam. 

So far, steam has been treated with sole reference to 
its warming and distributing facilities. Objection is 
sometimes made to steam heating that it does not furnish 
sufficient yentilation. To this it may be answered that 
the same is true of any method of heating simply as 
such 

It has already been explained how heating and venti- 
lating are antagonistic processes, ventilation always being 
at the expense of heat. In any method of heating venti- 
lation must be provided for and arranged as an accessory 
to the heating. No heating apparatus is in itself a venti- 
lator. Good ventilation is possible with any system of 
heating, as no yentilation at all frequently accompanies 
good methods of heating when by themselves considered. 

That poorly yentilated school-houses are sometimes 
heated by steam is no argument against steam as a method 
of warming ; nor does it proye that good yentilation is 
not possible with steam heating. This will soon be made 
apparent in the consideration of the different methods of 
steam heating, which are of three kinds, viz., heating by 
direct radiation, by indirect radiation, and by direct- 
indirect radiation. Heating with hot water is not well 
adapted to school-buildings, which are occupied only at 
intervals. This method, therefore, while possessing su- 
perior advantages for warming private dwellings, will not 
be here considered. 



STEAM HEATING. 137 

Direct Radiation, — In direct radiation the coils of 
steam-pipe or radiators are placed within the room to be 
warmed. They warm the air of the room by radiation 
and convection, and do j^recisely the work of a simple 
stove where heating is alone provided for and ventilation 
ignored. The single point of superiority of this method 
over that of the stove is in the comparatively large radi- 
ating surface and moderate temperature. As a mere 
heater, where the temperature of the room is alone con- 
sidered, no method is more effective, but when so used to 
the neglect of ventilation, heating by direct radiation 
alone can not he too heartily condemned. 

Enough has already been said concerning the evils of 
heating the air of a room without provisionjbeing made 
for frequently changing it. It needs only to be noted 
here that nothing is more certain to produce these evils 
than direct radiation when used alone. 

This must not be considered as an argument against 
direct radiation in itself, but hy itself ; indeed, it should 
form a part of every system of steam heating. It is here 
condemned only when used exclusively. When direct ra- 
diation is used in association with a good aspirating chim- 
ney, in which coils of steam-pipe may be placed to give a 
good draft, and when the radiators are so arranged that 
the cold air from the inlets will come in around them and 
be warmed before reaching the occupants of the room, it 
makes a fairly good arrangement. This is illustrated in 
Fig. 21, where D is the outside wall ; W, the window ; 
E, the cold-air duct ; E, the radiator ; A, the ventilating 
shaft ; B, the upper foul-air vent ; C, the lower foul-air 
vent. The arrows show the direction of the currents. 

This arrangement is commonly met with in school- 
houses, and is somewhat better than no provision at all 
for ventilation, but it is very inadequate. The heat can 



138 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

not by this means be properly distributed. If the outlet 
B is kept open, the warm unused air will escape ; if it is 



Fig. 21. 




kept closed, the foul air will accumulate in the top of the 
room. The radiator E, while good so far as it goes, does 
not warm the air sufiBciently as it enters to prevent cold 
drafts, providing the inlets are sufficiently large for the 
demands of ventilation. 

Steam heating by direct radiation, even without any 
provision for ventilation other than by windows, is preva- 
lent, almost discouragingly so. As a single illustration, 
the following words of John D. Philbrick, in his circular 
on '* City School Systems in the United States," may be 
used. In speaking of the high-school in the city of Wash- 
ington he says : ** It is to be regretted that the high-school 



STEAM HEATING. I39 

house recently erected in onr national capital should be 
in its planning so far behind the times. Its conspicuous 
absence of merit was not to have been anticipated, consid- 
ering the high reputation which the city had acquired for 
good school-house building in the erection of the Frank- 
lin and so many other good school buildings. . . . The 
heating is effected by means of direct steam radiation." 

Washington is here named because of its prominence 
and the common interests which center there ; but it is 
not the only city in which blunders have been made, and 
are being made, in school-house building relative to heat- 
ing and ventilating. In fact, the taking of Washington 
as typical is exceeding liberality toward other cities, some 
of which are really much worse. 

During the summer of 1886 I visited fhany school- 
buildings, with a view of studying their provisions for 
warming and ventilating. Among those which were 
warmed by direct radiation, several were arranged as rep- 
resented in Fig. 22, which is here given, as some of these 
buildings were new and may be supposed to represent the 
best that has been done in the localities where they were 
found. The figure shows the interior of a school-room 
with the two sides nearest the observer removed. R rep- 
resents the steam-pipes, extending along the sides of the 
room under the windows. S is a ventilatinof shaft in the 
corner of the room opposite the windows, made tight at 
the bottom, with no provision for heating the air inside 
of it. V is an outlet about one foot square, from the 
room into the ventilating shaft, and situated near the 
floor. No provision is made for air to enter the room ex- 
cept through the windows. 

The theory of this arrangement is diflBcult to guess, 
but the only one which approaches rationality is that the 
air is expected to rise from the pipes, move along the top 



140 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

of the room to the opposite corner, then to dive down to 
the bottom of the room and crawl up the shaft. This, 

FiCx. 22. 




while quite as reasonable as many current ideas concern- 
ing ventilation, is expecting altogether too much of the 
air, whose power of moving is passive and not active. 

The air will rise from the pipes to the top of the room. 
This is the only correct supposition in the above supposed 
theory. There is nothing to make it descend when it 
reaches the corner opposite, unless it is colder than the 
air below it, and what is to make it colder ? It may be 
at a temperature lower than when it started from the 
pipes, but it is still of a higher temperature than the air 
below it, in all parts not directly over the pipes. Hot air 
constantly rising to the top of an inclosed space will 
stratify along the highest plane, the warmest occupying 
the highest level. As the process continues the line of 



STEAM HEATING. 141 

demarkation between warm and cold air Avill descend 
lower and lower till the floor is reached, provided there is 
no outlet higher than the floor through which the warm 
air may escape. But in the present case there is such an 
opening, for the air is expected to enter at the windows, 
and where air can flow in when room is made for it within, 
it can also flow out when room is made for it without. 
Now, room will always be made for it without, when the 
windows are on the leeward side of the room. It has 
been previously explained how wind produces a partial 
vacuum on the leeward side of buildings or other obstruc- 
tions. The air inside will, therefore, have a tendency to 
flow outward on that side unless there is some counter- 
acting force inside to prevent it, and in th%present case 
there is none. Cross-currents will thus set in, and the 
windows will be both inlets and outlets. 

If this little foul-air shaft were converted into an as- 
pirating chimney of sufficient size in which heat could be 
easily supplied from coils of steam-pipe extended into it, 
there would be something to counteract this influence of 
the wind, as well as to furnish an adequate exit for foul 
air. In short, these little foul-air shafts, when so ar- 
ranged, are almost useless. They are not quite useless, 
because in cold weather, when the air is still, there will 
be a slight upward draft through them, due to the air in 
them being a little warmer than the outside air, but when 
the wind is blowing they are liable to become inlets. Di- 
rect radiation, with no other means than this for venti- 
lating or preventing cold drafts, is objectionable. The 
use of direct radiation, when accompanied with other pro- 
visions, will appear hereafter. 

Indirect Radiation.— In indirect radiation the pipes 
are not placed inside of the room to be warmed, but out- 
side in an inclosed chamber opening into the room and 



142 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

into the outside air. Tlie air in these chambers becomes 
heated, rises and passes into the room, and is followed 
by fresh cold air from outside the building. 

It is evident that a room warmed in this manner is neces- 
sarily partially ventilated, for the warming is not by ra- 
diation or convection, but from inflowing warm air, which 



Fig. 23 




must in entering displace an equal amount of air pre- 
viously in the room. 

This method of warming may be understood by ref- 
erence to Fig. 23, where a = outside wall of the house ; 
B = the fresh-air duct ; c the register opening into the 
room, and E the coils of steam-pipe. 



STEAM HEATING. 143 

Indirect radiation should be accompanied with ade- 
quate means for abstracting the foul air from the room, 
either in the form of a good aspirating chimney or a ven- 
tilating fan. Unless this be done, any form of indirect 
radiation will fail ; for, as two bodies can not occu])y the 
same space at the same time, the foul air must pass out 
before fresh air can pass in. A mere outlet into the open 
air will not generally suffice, for then the air must be 
pushed out by the air coming in from the radiators, a 
work which can not thus be adequately performed. 

The position of the radiators in a system of indirect 
radiation may vary according to local circumstances. 
Some builders, however, have a rule of placing them in 
the outside walls, and others in the inside walls near a 
central fresh-air shaft situated near the center of the 
building. Mr. Baldwin is of the former class, and gives 
as a reason for the outside position that, as the windows 
furnish a constant source of rapid cooling, a current of 
cold air is always passing down inside the room in front 
of them, thence along the floor, cooling the feet of the 
occupants. Placing the radiators in the outside walls 
under the windows furnishes an upward current of warm 
air which meets this cold current, thus counteracting it. 

Mr. Briggs, on the other hand, is of the latter class, 
and gives as reasons for interior locations of radia- 
tors : That basement piping is thereby saved ; that it 
obviates danger from freezing of pipes ; that it prevents 
loss of heat from introduction ducts or flues which run 
up the outer exposed walls of the building, and that the 
internal location makes it possible to place the inlets and 
outlets on the same side of the room, which it is claimed 
facilitates the bringing down of the warmed air from the 
top of the room, where it first rises, to the breathing line. 

Each of these plans of locating radiators possesses 
14 



144 VENTILATION AND WAKMING OF SCHOOL-BUILDINGS. 

some advantages over the other, but both are equally at 
fault on the one thing necessary to make steam heating 
perfectly successful. Both admit the warm air through 
a few large openings situated at the sides of the room, 
where it at once rises to the top before it is utilized. 
This, of course, necessitates the placing of the outlets 
near the floor, in order to retain the warm air till it has 
cooled sufficiently to descend and be used. The problem 
of distributing the warm air as it enters is not solved by 
either of these methods. Until it is solved, until the air 
can be so admitted that it can be utilized while on its 
way to the top of the room, so that when arriving there 
it may be let out at the ceiling, the place where Nature 
plainly dictates that its exit should be made, instead of 
trying to force hot air downward ; until this can be ac- 
complished, steam heating has little advantage in point 
of ventilation over some other systems. 



CHAPTER XIX. 

a:^ ideal plak for waemikg and ventilating. 

The necessary physical conditions of warming and 
ventilating have now been fairly well discussed. In our 
investigations of the different plans which have been em- 
ployed, the merits and demerits of each have been pointed 
out. While all have some characteristic points of excel- 
lence, none so far considered are without numerous and 
serious defects. Thus far no system has been devised 
that so distributes the air as it enters the room that it 
may be let out at the top — the place which Nature plainly 
dictates for its exit. No plan has yet been hit upon which 



AN IDEAL PLAN FOR WARMING AND VENTILATING. I45 

keeps the feet of the occupants warmer than the head — 
a necessity which the laws of blood-circulation make 
plainly evident. No system has yet been put in practice 
which does not at some point oppose the natural laws of 
ascent and descent. 

A device will now be described which I believe will 
not only remedy these defects but will comply with all 
the requirements of ventilation. In order better to esti- 
mate its yalue, let us first enumerate the requirements 
of ventilation. 1. The air must come from a pure source. 
2. It must be sufficient in quantity. 3. It must be 
warmed before being admitted into the room. 4. It 
must not be overheated. 5. It must be distributed as it 
enters, so that it may be utilized before it reaches the top 
of the room. 6. In order that this may b% possible, it 
must be admitted through the floor. 7. It must not be 
entrajoped in the top of the room. 8. The yentilation 
and air-supply must be independent of doors and win- 
dows. 

A careful study of the following figures will show how 
this may be accomplished. Fig. 24 shows the interior of 
a double chimney, with partition and side toward the ob- 
server removed so as to reveal the parts. B is the floor 
of a fresh-air shaft which constitutes one division of the 
chimney, as shown by the broken partition wall E G-. 
H is the opening into the large tube C, which carries 
fresh air to the rooms ; X X shows the front of this tube, 
cut away so as to show the other side. J J are floor- 
joists. A shows where the fresh-air tube sends off a 
branch directly under tlie floor of tlie first story ; F is 
the foul-air register, opening from the top of the room 
into the chimney. J' J' A' and F' show corresponding 
parts for the second story. A is the floor of the aspirating 
chimney, which contains the fresh-air tube just described, 
1 



146 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 




AN IDEAL PLAN FOR WARMING AND VENTILATING. I47 

and also the smoke pipes, P, which come from the fur- 
nace and extend to the top of the chimney. 

The action of this chimney exphiined is as follows : 
This chimney is to perform the work of ventilating and 
carrying the fresh air to four school-rooms. The large 
furnace pipe is divided into the several smoke pipes, P, 
so that the waste heat from the fire may be utilized in 
heating the air in the chimney, by making the heated 
radiating surface as large as possible. The air in this 
part of the chimney, thus heated, rapidly rises and creates 
a powerful upward draft, making a partial vacuum, which 
draws the foul air through the foul- air registers F at the 
top of the room. The smoke-joipes arc extended upward 
to the top of the chimney, to prevent the possible reflux 
of smoke which might otherwise occur in T^♦ndy weather. 
The heat from these pipes will also be communicated to 
the fresh-air pipe C ; and the fresli air which it contains, 
being thus warmed, will rise and pass under the floor 
through the branch tubes A and A'. It would probably 
be better to have the fresh-air tubes leading to the sepa- 
rate rooms independent of one another to avoid inequality 
of draft. In the figure two rooms are represented as be- 
ing supplied from one main pipe C, merely for conve- 
nience of illustration. The air thus rising in the tube C 
is followed by cold pure air from the fresh-air shaft B 
through the aperture H. This shaft, being a part of the 
chimney, extends to the top of the building, and there- 
fore brings the air from an elevated and pure source. 
The top of the fresh-air shaft should be several feet be- 
low the top of the smoke part of the chimney to avoid 
the drawing down of smoke. 

As we have seen in previous pages, this chimnc}^ must 
be large. There is little danger, under the present ar- 
rangement of conveying the smoke, of getting it too large. 



14,8 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

It should, if built for four rooms, have an area of cross- 
section of at least 64 square feet, making it equivalent to 
8 feet square. Summarized, a chimney thus constructed 
furnishes an outlet for smoke, for foul air, and an inlet 
for fresh air. The heat in it from the furnace has a ten- 
dency both to draw the foul air out and the pure air into 
the rooms, as explained. 

How, now, is the fresh air thus admitted beneath the 
floor to be warmed and distributed ? This may be un- 
derstood by reference to Fig. 25. J represents a series of 

Fig. 25. 




floor joists, and J' another series resting upon the first at 
right angles. This double arrangement is to give sufficient 



AN IDEAL PLAN FOR WARMING AND VENTILATING. 149 

room for the various radiating boxes necessary to perfect 
distribution. The inlet a corresponds to A and A' of Fig. 
24, and is the opening into the box B, extending along 
under one side of the room ; are openings or registers, 
opening from the large box B into smaller radiating boxes 
h, which extend along under the floor between the upper 
set of floor-joists \ s s are steam-pipes for further warm- 
ing the air as it enters. 

The heat from this source gives to the air already in 
motion another impulse in the same direction, upward 
through the floor register R, as indicated by the arrows, 
thus further increasing and securing constancy and steadi- 
ness of the air movement. 

The air, on thus entering, will be properly warmed, 
and being admitted at the floor will securt comfort for 
the feet. There should be a radiating box, b, for every 
row of desks, to deliver the air through registers situated 
at frequent intervals along the aisles. The warm air, tlius 
[)erfectly distributed, as it enters rises toward the ceiling, 
both by its own specific lightness due to temperature, and 
by its tendency to fill the vacuum produced at the top of 
the room from the draft of the aspirating chimney, as 
explained in Fig. 24. 

Here there can be no uncertainty about the disposition 
of CO2 and the organic emanations from skin and lungs. 
All of these impurities are carried off as fast as formed, 
both from a tendency which an animal temperature of 
98° gives them to rise, and the. constant stream of rising 
air into which they are poured. 

Steam-pipes should also be placed in the large radiat- 
ing box B, to aid both in warming the air and in increas- 
ing the strengtli and steadiness of the movement. These 
boxes should be made of wood and lined with tin. F is 
the floor of the room. At there should be a damper 



150 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 



for regulating the draft, and controlled by a lever ex- 
tending up through the floor. The opening, a, should 
be large, as the amount of air delivered through it is 
great. The form and proportion are of course not speci- 
fied in the figure, which is only intended to make the 
principle of the movement understood. 

What, now, it may be asked, will prevent the space 
beneath the floor from filling with dirt through the floor 
registers ? This is answered in Fig. 26, which represents 

Fig. 26. 




\j o u^ o o 

(if d X d 1 d. . d 




a cross-section through a portion of the floor, the radiat- 
ing box, and containing steam -pipes. F shows the 
floor ; r the connecting box-riser ; I? §, the radiating box ; 
ss Sy the steam-pipes ; and 1 1, the lid of the register in 
the space fitted for it in the floor. 

The peculiar shape of this lid, as represented, will be 
sufficient to suggest how the dirt is prevented from fall- 
ing into the box. Everything which falls through the 
spaces at the top of the lid will be received by the loops 
at d. The arrows indicate the direction of the air through 
the numerous holes made in the perpendicular sides of 
the several loops. Floating dust will have no tendency 
to enter these holes, because the current of air will pre- 



AN IDEAL PLAN FOR WARMING AND VENTILATING. 151 

vent it, being from the direction to drive it away. These 
lids, made of light castings, will not be expensive, and 
can be easily raised out and freed from dirt, which from 
time to time will accumulate in the loops. 

The two sets of lioor-joists which this system necessi- 
tates will incur some additional expense, but this will be 
slight when the accompanying advantages are considered. 
The greater space which the double arrangement would 
require would not necessitate any increase in the height 
of the building, for it is plain that when rooms are venti- 
lated as above described, the height of the room is not 
important. The number of cubic feet of air space for 
each pupil loses importance as perfect ventilation is ap- 
proximated. Thousands of people may stand crowded 
together in the open air and all be provideft with pure 
air. This is simply because the ventilation of Nature is 
perfect. The heated emanations from the body rise and 
fresh air comes in from all sides to fill the partial vacuum. 
This is the method above proposed. The movement of 
all the air in the room is upward, with ample provision 
for the supply of plenty of fresh warm air from below. 

Thus far we have considered ventilation with reference 
to the requirements of winter, or when artificial heat is 
required to raise the internal temperature of the rooms 
above that of the outside. In the fall and spring, when 
no extra heat is needed in the rooms — when the internal 
and external temperatures are nearly equal — it is then 
only necessary to heat the air in the foul-air compartment 
of the chimney in order to maintain a draft sufficient to 
abstract the foul air as fast as formed. There are several 
ways to do this. A stove may be set at the bottom of the 
chimney, or coils of steam-pipe may extend into it from 
the boiler. For the system we are considering this is the 
jiroper method of heating the chimney in warm weather. 



152 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

By means of valves the steam may be shut off from all 
the radiator pipes, allowing it to pass only through the 
pipes in the chimney. And, owing to the manner in 
which the heat of the smoke and the waste products of 
combustion are utilized, the necessary heat could be by 
this means most economically produced. 

This heating of the chimney in warm weather should 
not be neglected. It is commonly supposed that in warm 
weather, when the windows may be opened, ventilation is 
easily secured. This is a great mistake. It is easier to 
ventilate in winter than in summer. In cold weather the 
inequality of internal and external temperature is in itself 
a cause of movement, as heretofore explained ; but when 
the internal and external temperatures are nearly equal, 
change of position takes place (in the absence of wind) 
only by diffusion. 

In order to suit the conditions of cool weather, when 
a little heat is needed, the pipes extending through the ra- 
diators should be connected in sections, so that steam 
could be shut off from any number of them as desired. 
For instance. Fig. 27 shows a main supply pipe, sending 
off branches which are again subdivided, each sending a 
pipe to the several radiators. Thus, section A sends one 
pipe through each radiating box in the building ; section 
B another, section another. When only a third of the 
usual amount of heat is required, all the valves are closed 
except 0, through which steam will then alone be admit- 
ted. If more heat is needed, open valve B. In coldest 
weather, open all. For the severest weather, in high lati- 
tudes, a section should be set apart leading to direct ra- 
diators placed in the rooms. By skillful management of 
the details any temperature may be secured and ventila- 
tion be equally good in all seasons. 

Another advantage which the double set of floor-joists 



AN IDEAL PLAN FOR WARMING AND VENTILATING. 153 

secures is in the effectual deadening of sound which 
the enlarged space would secure. In all school-houses of 

Fig. 27. 




two or more stories some means of deadening the sound 
of moving feet, conducted through the floor and ceilmg 



154 VEXTILATION AND WARMING OF SCHOOL-BUILDINGS. 

to the room below, is absolutely essential. Where this is 
effectually done, the cost will exceed that of th6 double 
joists. This system of warming and ventilating, it ap- 
pears to me, answers all the requirements of ventilation : 
1. The air taken from the height of the building is from 
a pure source. 2. From the large size of the chimney 
and fresh-air shaft, this air is sufficient in quantity. 3. 
By the distribution of steam-pipes as described it is 
warmed before being admitted into the room. 4. By a 
proper apportionment of these pipes the air need not be 
overheated. 5. By the numerous small registers distri- 
bution is perfect. 6. It is through the floor, thus secur- 
ing the warmth of the feet. 7. It is not entrapped in the 
upper part of the room, but rapidly hurried away from 
this point. 8. The inlets and outlets being of ample size, 
and the velocity of the air sufficient, the ventilation will 
be independent of doors and windows. 

On the latter point too much stress can not be laid. 
Open doors and windows, especially in a city, are a source 
of great annoyance. The rattle of passing vehicles, the 
din of machinery and steam- whistles, sometimes render it 
impossible to hear a recitation. In windy weather great 
clouds of dust from the streets, and smoke from neigh- 
boring chimneys, pour in through open windows to com- 
plete the discomfiture of all helpless victims of window 
ventilation. In winter, where windows are relied upon, 
currents of icy cold air pour in, endangering the lives of 
pupils ; while currents of warm air pour out, sometimes 
before it has been utilized. 

It will doubtless be a surprise to many that the fresh- 
air shafts and chimneys for foul air need to be so large ; 
but a careful perusal of the foregoing pages will convince 
the intelligent reader that there is no help for this if any- 
thing like perfect ventilation is approximated. Facilities 



AN IDEAL PLAN FOR WARMING AND VENTILATING. I55 



g 



for yentilation are to a house what lungs are to an ani- 
mal. They must be capacious and active, to maintain a 
healthy and vigorous life. The ventilating and warming 
apparatus constitute the vital organs of a building, and 
are therefore of first importance in school-house building. 
Utility first and ornamental finish last. Where utility 
and architectural symmetry conflict, the latter should 
give way to the former. Give us life first and beauty 
second. However, it need not be supposed that sym- 
metry is necessarily sacrificed or school-room capacity in- 
terfered with by the use of these generous chimneys. 

The three essential qualities of a school-house, named 
in the order of their importance, are utility, simplicity, 
and beauty. If these qualities are attended to in the or- 
der here named, all three are possible of attainment ; but 
if the order be reversed, as is commonly the case, only 
the first — beauty — will be attained. 

In a two-story building one chimney should not be 
required to serve more than four rooms. If three stories, 
it may supply six rooms. A peculiarity of this system of 
ventilating is that the higher the building the greater is 
its efficiency. The reason for this is evident. The draft of 
a chimney is not only always increased with its height, but 
in this case the higher the building the farther the fresh- 
air tubes will extend upward through the heated air of the 
aspirating chimney. This not only adds still more power 
to the draft, by the additional heat given to the ascending 
fresh air, but this heat is utilized in giving additional 
warmth to the air before it enters the radiators. 

There are many designs which might be made, where- 
by all the qualities of a good school-house are secured. 
An original plan is suggested in Fig. 28, which may be 
considered the first story either of a two or three story 
building. If two stories, there will be sixteen rooms ; if 
15 



156 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 




REFERENCE. 

A. Foul air and smoke,. 

B. lYesh air. 



AN IDEAL PLAN FOR WARMING AND VENTILATING. 157 

three stories, twenty-four rooms. This is as many rooms 
as will commonly be found necessary in a single buildmg. 

The plan is self-explanatory. The spaces between the 
rooms serye the purposes of fresh air, foul air, smoke, 
water-closet, and hat- room. The water-closet adjoins 
the foul-air part of the chimney. An opening through 
the dividing wall will effectually ventilate the closet. A 
is the smoke and foul-air part of the chimney, and B 
the fresh-air shaft ; the latter communicating with the 
former, as shown in Fig. 24. The combined chimney 
and fresh-air shaft should have at least 64 square feet 
sectional area. It may be made by this plan of almost 
any size without inconvenience or sacrifice of symmetry. 
Iron ladders should be secured on the inside of both com- 
partments of the chimney to facilitate the adjttetment and 
repair of the various pipes. 

One half of this design makes a plan for an eight- 
room building. Eight rooms is generally preferable to 
any other number. For this arrangement not only gives 
unobstructed light on two sides of each room, but more 
easily meets architectural requirements, and is sufficient 
to serve the ends of ordinary graded school-work. The 
large plan is here given to answer the requirements in 
large aift crowded cities where the economy of space re- 
quires as few buildings as possible, and for high-school 
buildings where eight rooms are sometimes insufficient to 
serve the demands of the proper specialization of the 
various departments. 

Fig. 29 is a plan illustrating how the same qualities 
may be secured in a building of 6 or 12 rooms. 

The advantages which these plans secure are : 1. The 
whole building is perfectly warmed and ventilated. 2. 
There is light on two sides of each room. 3. The chim- 
neys are out of the way and do not project into the school- 



158 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

rooms. 4. There is plenty of blackboard room on plane 
surface unbroken by ad jut ting chimneys and a multi- 
plicity of windows. 

Let it be noted here that narrow hat-rooms are gen- 

Fia. 29. 




REFERENCE. 

A. FouJ air and smoker 

B. Fresh air., 

C. Closet. ' 



erally a nuisance, and a source of crowding and disorder 
at dismissal. The halls should be wide, with a stationary 
hat-rack extending along each side about three feet from 
the wall. This arrangement gives not only plenty of room 
for hats and wraps, but makes them accessible. The small 
hat-rooms in the foregoing plan are given not so much to 
meet any real necessity for them, as to utilize space which 



AN IDEAL PLAN FOR WARMING AND VENTILATING. 159 

would otherwise be useless. By using them as merely 
supplementary to the hall space, crowding in them may 
be avoided. 

These, it appears to me, are some of the essentials of 
a school-house. I leave the superficial embellishments to 
the taste of the architect. Towers, turrets, buttresses, 
cantilevers, balustrades, consoles, corbels, scrolls, cupolas, 
pilasters, pendants, paint, and colored glass are of later 
consideration. These are all useful after the essentials 
are first secured. They are educative, and should be en- 
couraged to the full extent of the remaining means for 
procuring them after the vital organs have been intelli- 
gently planned and skillfully adjusted. 

Note. — A patent on this system has been applied for. 



APPEIJDIX. 



A. 

By a long and laborious series of observations with 
hygrometers and dry- and wet-bulb thermometers, Mr. 
Glaisher deduced empirically a series of factors which are 
of inestimable value in testing the humidity of the air by 
means of the wet and dry bulbs. To use these factors, 
multiply the difference between the dry and wet bulb 
readings by the factor which stands opposite the dry bulb 
temperature, and the product subtracted from the dry 
bulb temperature will give the dew point. 

Let t = temperature of dew point. 

*^ f= '' *^ dry bulb. 

'' t^—. '' *^ wet bulb. 

'* ^ = factor. 
We then have the formula 

t=:t^-(f-^t^)k (1.) 



APPENDIX A. 



161 



GLAISHER'S FACTORS. 



Reading 




Reading 




Reading 




Reading 




of dry 


Factor k. 


of dry 


Factor k. 


of dry 


Factor k. 


of dry 


Factor k. 


bulb. 




bulb. 




bulb. 




bulb. 




10° 


8-78 


33° 


3-01 


66° 


1-94 


79° 


1-69 


11 


8-78 


34 


2-77 


57 


1-92 


80 


1-68 


12 


8-78 


35 


2-60 


58 


1 90 


81 


1-68 


13 


8-77 


36 


2-50 


59 


1-89 


82 


1-67 


14 


8-'r6 


37 


2-42 


60 


1-88 


83 


1-67 


15 


8-75 


38 


2-36 


61 • 


1-87 


84 


1-66 


16 


8-70 


89 


2-32 


62 


1-86 


85 


1-65 


11 


8-62 


40 


2-29 


63 


1-85 


86 


1-65 


18 


8-50 


41 


2-26 


64 


1-83 


87 


1-64 


19 


8-34 


42 


2-23 


65 


1-82 


88 


1-64 


20 


8-14 


43 


2-20 


66 


1-81 


89 


1-63 


21 


'7-88 


44 


2-18 


67 


1-80 


90 


1-63 


22 


'7-60 


45 


2-16 


68 


1-79 


91 


1-62 


23 


7-28 


46 


2-14 


69 


1-78 


92 


1-62 


24 


6-92 


47 


2-12 


70 


1-77 


93 

*94 


1-61 


25 


6-53 


48 


2-10 


71 


1-76 


1-60 


26 


6-08 


49 


2-08 


72 


1-75 


95 


1-60 


2Y 


5-01 


50 


2-06 


73 


1-74 


96 


1-69 


28 


5-12 


51 


2-04 


74 


1-73 


97 


1-59 


29 


4-63 


52 


2-02 


75 


1-72 


98 


1-58 


30 


4-15 


53 


2-00 


76 


1-71 


99 


1-68 


31 


3-66 


54 


1-98 


77 


1-70 


100 


1-57 


32 


3-32 


55 


1-96 


78 


1-69 







The elastic force of vapor of water increases with the 
temperature. If, then, the elastic force of vapor of water 
at the temperature of saturation (dew point) be divided 
by the elastic force of vapor at a given temperature, the 
quotient will express the ratio of humidity to saturation. 
The following table shows the elastic force of vapor of 
water, measured in inches of mercury : 
Let t = temperature of dew point. 

*^ R = ratio of humidity. 

" jt? = elastic force of vapor at temperature T. 

" T = temperature of the air. 

'^ p' = elastic force of vapor at temperature i (dew point). 

ThenR = ^' (2.) 



162 VENTILATION AND WARMING OF SCHOOL -BUILDINGS. 



Tempera- 
ture of 
the air. 


Force of 
vapor in 
inches of 
mercury. 


Tempera- 
ture of 
the air. 


Force of 
vapor in 
inches of 
mercury. 


Tempera- 
tiu-e of 
the air. 


Force of 
vapor in 
inches of 
mercury. 


Tempera- 
ture of 
the air. 


Force of 
vapor in 
inches of 
mercury. 





P 
0-044 


rpcs 

24 


V 
0-129 


mo 

48 


P 

0-335 


rpo 

72 


P 

0-785 


1 


0-046 


25 


0-135 


49 


0-348 


73 


0-812 


2 


0-048 


26 


0-141 


50 


0-361 


74 


0-840 


8 


0-050 


27 


0-147 


51 


0-374 


75 


0-868 


4 


0-052 


28 


0-153 


52 


0:388 


76 


0-887 


5 


0-054 


29 


0-160 


53 


0-403 


77 


0-927 


6 


0-057 


30 


0-167 


54 


0-418 


78 


0-958 


7 


0-060 


31 


0-174 


55 


0-433 


79 


0-990 


8 


0-062 


32 


0-181 


56 


0449 


80 


1-023 


9 


0-065 


33 


0-188 


57 


0-465 


81 


1-057 


10 


0-068 


3t 


0-196 


58 


0-482 


82 


1-092 


11 


0-071 


35 


0-204 


59 


0-500 


83 


1-128 


12 


0-074 


36 


0-212 


60 


0-518 


84 


1-165 


13 


0-078 


37 


0-220 


61 


0-537 


85 


1-203 


14 


0-082 


38 


0-229 


62 


0-556 


86 


1-242 


15 


0-086 


39 


0-238 


63 


0-576 


87 


1-282 


16 


0-090 


40 


0-247 


64 


0-596 


88 


1-323 


17 


0-094 


41 


0-257 


65 


0-617 


89 


1-366 


18 


0-098 


42 


0-267 


66 


0-639 


90 


1-401 


19 


0-103 


43 


0-277 


67 


0-661 


91 


1-455 


20 


0-108 


44 


0-288 


68 


0-685 


92 


1-501 


21 


0-113 


45 


0-299 


69 


0-708 


93 


1-548 


22 


0-118 


46 


0-311 


70 


0-733 






23 


0-123 


47 


0-323 


71 


0-759 







Example 1. — Supj)ose the temperature of the room as 
indicated by the dry bulb to be 72° ; the temperature of 
the wet bulb 68°. Required the temperature of the dew- 
point, and the degree of humidity. In formula (1) f = 
72° ; t' = 68°; /^ = 1-75 ; then, t = 72° - (72° - 68) 
1-75; 2^ = 47-5°. 

In formula (2) p', for 47*5° = 0-323 ; p, for 72° = 

0*785 ; R = ^ = = -40 (per cent of saturation). 

This shows an atmosphere somewhat too dry. The de- 
grees of difference between the dry and wet bulb readings 
which should exist in order to conform to any required 
standard may be shown by the following: 



APPENDIX B. 1(J3 

Example 2. — If the temperature of the room as shown 
by the dry-bulb thermometer be 72°, what should be the 
temperature of the wet bulb in order to conform to the 
provisional standard of humidity given by de Chaumont, 
73° ? From formula (2) p' z=^p= -73 X '785 = -573. 
The degree in the table corresponding to this number is 
63°. This is the dew point corresponding to our standard. 

From formula (1) f = *+l^-^ = ^_m\i^l^^3=J3 

Ic 1*75 

= ^Q, the number of degrees which should be shown by 

the wet bulb when the dry bulb shows 72°. 



B. * 

Aspirating chimneys and ventilating shafts are some- 
times employed to counteract the force of the wind, to 
increase the velocity of the flow of air into the room by 
means of a fire in the chimney, to warm the air before it 
enters the room, and to draw the air from an elevated 
source to insure purity. The following, Fig. 30, illus- 
trates a simple form, sufficiently accurate to illustrate the 
use of the formulas, though not ideally correct as to the 
relative position and number of openings. Eeference : 
1, "entrance shaft ; 2, horizontal air-ducts ; 3, room ; 4, 
aspirating chimney ; 5, grate. We have here, in addition 
to the conditions before given, an acceleration in the ve- 
locity of the air entering the room due to the aspirating 
power of the chimney ; increase of temperature in the 
chimney by fire ; and friction due to the surfaces and 
angles in the air-passages. The co-efficients of friction 
used by engineers are as follows : Tn ducts, 0*024 ; for 
rough flues, 0*05 ; for brick flues, 0*05 ; for square elbow. 



164 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

1'50 ; for circular elbow, 0*50 ; air passing from a larger 
to a smaller flue, '50 ; air passing through a wall or plate. 



1 i 



Fig. 30. 



^S^^^^^^2^Si^^^SSSS2^^^^^^^^^^23^ 



g^I^ 



Et^TT^^ 



:\\'^\\^V^Kx\xVxyA^\x^\Vx^V^\^VVVVVV^V^^VvVxvsM-kVVVV^VVV^KVVVVKV^^^^^^ 



0'50 ; air passing from a smaller to a larger flue through 
an opening in the wall, Fig. 31. Eeference : A, A^, A^ 



Fig. 31. 




= areas of flues ;/= co-efficient of friction, in ducts; 
p = co-efficient of friction in elbows ; 



APPENDIX B. Ig5 

A . )2 



a=-QO whenA > A^f'= j^- l[ , 
when A^ = A2 < A, /I = -j A _ 1 [\ 



When the angle of a tube, ventilating shaft, or other air- 
passage is not 90° the conditions of any angle between 
and 180° may be approximately expressed by the formula : 

1 I cos _^ 

^ . With these new elements, and from the fact 

that the velocity is inversely proportional to the square 
root of the friction, and that for similar cross-sections 
the friction is inversely as the diameter, we have the 
following, another modification of Montgolfier's for- 
mula : 



V 



=vq 



+"' i+f^+r 



where V = velocity of air in feet per second in ducts. 

e = expansion of air for 1° Fahr., '00203. 

t = external temperature. 

t^= internal temperature of the chimney. 

I = length of ducts, including h -\- h^ -^ l^ -{■ f, 

f = co-efficient of friction in ducts. 
f^ = co-efficient of friction in elbows. 

g z= acceleration due to gravity = 32 '166 feet. 

d = diameter of ducts. 

h^ = height of aspirating chimney. 
h^ = height of entrance chimney. 

h = total height of chimneys, 
Uxample. Sui^^ose that t^ => 100° ; t = 60 ; I = h -{- 
^2 + Z^ -f Z2 = 80 + 30 + 8 -f- 8 = 126 feet ; h=SO;f = 
•05 for brick flues ; f^ for 2 square elbows = 1*5 X 2 = 3 ; 
d = S. Then: 



166 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 



y= ./ •002Q3(10Q— 6 0) 2 X 32-16 X 50 _ 

^ 1 + -00203 X 60" ' -, , n;c 13^ 1 Q ~ 

1+ 05-^ — 1-3 



v1 



0812 X 5145-6 _ /417 -83373 _ 

:a318 X 6-366 - ^ 'roWlT - ^59-44 = 7-7 feet 
per second. This, being the rate at which the air passes out 
of the room, may also be taken as the rate passing in. It 
thus appears that where the friction is considerable the 
aspirating chimney, or other means of accelerating the 
movement of air, becomes a necessity. 



0. (See page 84.) 

The following formulas, taken from Schumann's 
''Manual," will be useful in determining the size and 
construction of the various parts of the fan : 
Reference : 

V = volume of air delivered in cubic feet per second. 

h = height of manometer. 

c = velocity of air entering the fan. 

Ci= velocity of air leaving the fan. 

r = outer radius of vanes. 

ri= inner radius of vanes. 

r2= radius of inlet. 

h ■= width of vanes. 

a — height of outlet. 

«i= distance from vertical radius to point e (see Fig. 14). 

n = number of revolutions per minute. 

p = radius of a circle whose diameter is unity = 3*1416. 

^2= i/ — , where there is one inlet. 
^ cp 

^2= i/ - — , where there are two inlets. 
^ 2cp 



APPENDIX D, 107 



h = zr- , where there is one iiilefc. 
2 7-1 

b = — , where there are two inlets. 
r 

V 

2636 /^ V 

w = Vh : a = ^ — ; 

r oci 

«i= 0*159 a. 



D. 

COiq"DUCTIKG POWEK OF MATERIALS. 

Value c, being the units of heat transmitted per hour 
per square foot of a plate 1 inch thick, the ts^ surfaces 
differing in temperature 1°. 

c = 

Copper 515-000 

Iron 233-000 

Zinc 225-000 

Lead 113*000 

Marble, gray, fine grained 28 -000 

Marble, white, coarse grained 22 -400 

Stone, calcareous, fine 16*700 

Stone, calcareous, ordinary 13 '680 

Glass 6-600 

Brick- work, baked clay 4-830 

Plaster, ordinary 3 -860 

Oak, perpendicular to fibers 1*700 

Walnut, perpendicular to fibers 0*830 

Pine, perpendicular to fibers 0*748 

Pine, parallel to fibers 1-370 

Walnut, parallel to fibers 1 *400 

16 



168 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

Gutta-percha 1 -380 

India-rubber 1-370 

Brick-dust, sifted 1-330 

Coke, pulverized 1 -290 

Cork / 1-150 

Chalk, in powder 0*869 

Charcoal of wood, powdered 0*636 

Straw, chopped '563 

Coal, small sifted 0-547 

Wood-ashes . . . , 0-531 

Mahogany dust -523 

Canvas of hemp, new -418 

Calico, new 0*402 

Writing-paper, white -346 

Cotton or sheep's wool -323 

Eider-down 0*314 

Blotting-paper, gray 0*274 

For double windows, when the glass is not less than 2 
inches apart, c = 3 '6. 

Stagnant air, c = 0'3, 



E. 

Value of r, being the radiating and absorbing power 
of bodies, in units of heat per square foot, for a difference 
of 1° Fahr., from the experiments of Piclet : 

r = 

Silver, silvered copper 0*02657 

Copper 0-03270 

Tin 0-04395 

Zinc and brass, polished 0*04906 



APPENDIX F. 169 

r = 

Iron, tinned 0*08585 

Iron, sheet 0-09200 

Iron, ordinary 0*56620 

Iron, cast, new 0*64800 

Iron, sheet and cast, rusted. 0*68680 

Lead, sheet *13286 

Glass 0*59480 

Chalk 0*67860 

Wood sawdust, fine 0*72150 

Building stones, plaster, wood, brick . . 0*73580 

Sand, fine 0*74000 

Calico 0*74610 

Woolen stuffs 0*75220 

Silk stuffs, oil paint 0-t5830 

Paper 0*77060 

Lampblack 0*81960 

Water 1-08530 

Oil 1*48000 



F. (See page 87.) 

The Blachman Fan. — My invention is a ventilating- 
fan, constructed, as fully described hereinafter, so as to 
rapidly transmit motion to large volumes of air, carrying 
the same in solid columns without dispersing it or creating 
back currents. 

In the drawings. Fig. A (see page 87, Fig. 13) is a near 
view of a ventilating-fan with my improvements. Fig. B 
is a section on the line 1, 2, Fig. A. Figs. C to G (Fig. 
32, page 170) are diagrams illustrating the formation of 
the blades. Fig. H, a perspective view of a blade and the 
hub. 



170 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 






Fig. 82. 



^ 


1 


^^-^ ^ 



V 



A \y 



D 



Flni.O 




APPENDIX F. 171 

In experimenting with that class of fans used to put 
air in motion for ventilating and other purposes, I ascer- 
tained that, in ordinary constructions, while volumes of air 
would be driven forward by the revolution of the fans, other 
volumes would be thrown off radially, and still others 
would be thrown backward instead of forward, as desired, 
creating currents interfering with the free flow of air to 
the fan. After many experiments I ascertained that by 
bending each blade outward at the upper end, forming per- 
ipheral sections, thus compelling the large volumes ordi- 
narily dissipated in this direction to move directly forward. 

My present invention relates to certain improvements 
whereby I have succeeded in preventing altogether any 
back-flow, insuring a forward propulsion of all the air 
coming within the influence of the wheel. * 

In the course of my experiments I ascertained that it 
was necessary to so construct each blade of the wheel as 
to draw or deflect outward the air from the forward edge 
of every portion of the blade, and to set every portion or 
face of the blade at such an angle that the forward edge 
at every point would " cut under " the air rather than 
move it laterally or carry it with the wheel, and that 
while portions of the blade might be so bent as to throw 
the air outward, other portions, if not properly shaped, 
would draw it back, creating counter currents. I found 
that to prevent such results it was essential to vary the 
angle and curve of the blade at different points, and that 
although such angles and curves would be different, ac- 
cording to the sizes of the wheels and number of blades, 
there were certain definite and specific proportions and 
forms common to all, which result in much improved 
effects, and which I will now specify. 

The hub A of the wheel may be solid, or may consist 
of disks a a' secured to the shaft B. From the hub ex- 



172 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 

tend radial ribs h, wliicli meet an annular rim c, and 
said ribs constitute the straight edges of the blade D, the 
rim c and ribs being all in the same vertical plane x. The 
diameter of the hub A and the depth of the wheel should, 
to secure the best results, be about equal to one sixth of 
the diameter of the wheel, and the ribs or edges d, instead 
of being radial, should coincide with lines extending from 
the periphery, through the hub, midway between the axis 
and periphery of the latter. The blades, instead of being 
set with their inner ends parallel to the axis, join the hub 
upon lines y y, crossing the axial line at an angle at the 
center, and the forward edge of each blade corresponds to 
a curye which is gradually increased toward the outer 
end, the edges of all the blades being upon a plane z z, 
parallel to the plane x x. Thus the forward edge of each 
blade may be a rib, e, extending from the hub nearly par- 
allel for a short distance with the rib 1), and then curved 
forward until it nears the periphery, when the curve is 
sharper, as shown. The body of the blade, between the 
edges or ribs h, e, is gradually bent at an angle which be- 
comes more and more obtuse to the axis of the shaft as it 
approaches the periphery, as shown in fine lines. Fig. 0, 
and is also bent from a perpendicular line, parallel to the 
edge h, as it recedes from said line toward the edge e, as 
shown in dotted lines, Fig. A. At the periphery the 
blade is bent to form a peripheral section, d, that extends 
from the blade to the rim c, and has a forward edge, t, 
parallel to the axis of the shaft. This peripheral section 
may form part of the blade, or may be a separate piece 
riveted or otherwise secured thereto. If the blade were 
bent or hollowed from each end to the center, as shown 
by the outline. Fig. D, the air collected by the ends of 
the blade, instead of being carried outward, would be 
drawn to the center and thrown backward in currents. 



APPENDIX F. X73 

interfering with the flow of air to the wheel ; so, if the 
Made at any point, as at the hub. Fig. E, is too nearly 
parallel with the axis of the shaft, the air, instead of be- 
ing sent forward, will be carried round with the wheel, 
and the effect will not be proportioned to the power ex- 
pended. By setting the blade at an angle to the axis, as 
shown in Fig. 0, by maintaining the portion near the 
hub comparatiyely flat, by bending the body beyond the 
center, and by giving a sharper curve thereto near the 
periphery, where it meets the peripheral section, as de- 
scribed, I have succeeded in preventing any back-flow, 
and have with comparatively little power imparted move- 
ment to large volumes of air in one direction, and in 
nearly solid columns. This effect is increased by setting 
the blade somewhat tangential to the axis, a^ described, 
instead of radially, the outer end thus being pitched for- 
ward, so as to draw in the air, instead of dispersing it 
radially. This will be best understood on reference to 
diagrams Figs. F and Gr, in which diagram F illustrates 
a radial blade which throws out the air by its revolution, 
while diagram Gr represents a blade set tangentially to 
the hub, and tending to draw the air toward the latter. 
It will be evident that the ribs d e may be flanges formed 
by bending the edges of the blades. 

It is common to set ventilating-fans in openings in 
walls or frames, which completely surround the periph- 
eries of the fans and prevent any radial inflow of air. I 
set my fan back so that the front face will be nearly on the 
same plane as the inner surface, w, of the wall or frame, 
as shown, thus permitting a free flow of air to the pe- 
riphery (see Fig. 13). 

THE EKD. 



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WITH DETAILED EXAMPLES, AND AN INQUIKY INTO THE DEFI- 
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Johonnot's Principles and Practice of Teaching. 

This is a practical book by an experienced teacher. The subject of education 
is treated in a systematic and comprehensive manner, and shows how rational 
processes may be substituted for echool-room routine. Price, $1.50. 

Baldwin's Art of School Management. 

This is a very helpful hand-book for the teacher. He will find it full of prac- 
tical su2;gestions in regard to ail the details of school-room work, and how to 
manage it to best advantage. Price, $1.50. 

Greenwood's Principles of Education Practically Applied. 

The object of this work throushout is to impress this important question 
upon the mind of the teacher: '''How shall I teach so as to have my lywpils 
become self-reliant^ independent^ manly men and womanly women f"" Price, 
$1.00. 

Sully's Outlines of Psychology, 

WITH SPECIAL REFERENCE TO THE THEORY OF EDUCATION. 
Price, $3.00. 

Sully's Hand-Book of Psychology, 

ON THE BASIS OF OUTLINES OF PSYCHOLOGY. A practical exposi- 
tion of the elements of Mental Science, with special applications to the Art 
of Teaching, designed for the use of Schools, Teachers, Reading Circles, and 
Students generally. Price, $1.50. 

Bain's Moral Science. 

A COMPENDIUM OF ETHICS. Divided into two divisions. The first— 
the Theory of Ethics — treats at length of the two great questions, the ethical 
standard and the moral faculty : the second division— on the Ethical Systems 
— is a full detail of all the systems, ancient and modern, by conjoined abstract 
and summary. Price, $1.50. 

McArthur's Education, 

IN ITS RELATION TO MANUAL INDUSTRY. The important subject 
of manual education is thoroughly and clearly treated. Price, $1.50. 

Hodgson's Errors in the Use of English. 

A work for the teacher's table, and invaluable for classes in grammar and 
iiterature. Price, $1.50. 

Descriptive Catalogue sent free on application. Special prices will be made on 
class supplies. 

D. APPLETON & CO., Publishers, 

New York, Boston, Chicago, Atlanta, San Francisco. 



k NEW AND CAREFULLY REVISED EDITION OF 

john stuart mill's 

Principles of Political Economy. 

Abridged, with Critical, Bibliographical, and Explana- 
tory Notes, and a Sketch of the History 
of Political Economy. 

By JAMES LAURENCE LAUGHLIN, Ph. D., 
Assistant Professor of Political Economy in Harvard University. 



With Twenty-four Maps and Charts. 8vo. 658 pages. 
Cloth, $3.50. 



No writer on Political Economy, since Adam Smith, the acknowledged 
father of Political Science, can be compared in originality, exact and forcible 
expression, and apt illustration, to John Stuart Mill. His writings on this 
great subject, while practical and popular in their adaptation, are also 
characterized by the true philosophic method. In his knowledge of facts 
and conditions, his clearness of understanding, and the soundness of his 
reasoning, he excels all other writers on the subject, and his " Principles 
OF Political Economy " has been an unfailing source of information and 
authority to all subsequent writers and students of political science. 

To present this work in form, size, and method, somewhat better adapted 
to class-room use, and present modes of study, and at the same time to 

E reserve it so far as possible in the form and language of its great author, 
as been the aim in the present revision. The editor has made this work 
essentially a revision, and not a systematic mutilation. The publishers 
therefore feel confident that the new edition will be found thoroughly 
adapted to class use, and as such will prove a valuable and satisfactory text- 
book, and at the same time will be found to retain and present all the 
essential and valuable features of the original work. 

The new edition retains, in its own clear exposition, the connected sys- 
tem of the original, and at the same time its size is lessened by omitting 
what is Sociology rather than Political Economy. The difficulties of the 
more abstract portions of the original work are much lightened, and the 
new edition presents, in connection with the general tenor of the work, 
some important additions of later writers. 



For sale hy all booksellers ; or sent by mail, post-paid, on receipt of price. 



New York: D. APPLETON & CO., Publishers, 1, 3, & 5 Bond Street. 



EDUCATION IN RELATION TO 
MANUAL INDUSTRY. 

By Arthur MacArthur, LL. D. 12mo. Cloth, $1.50. 

*'Mr. MacArthur's able treatise is designed to adapt to the usual methods of 
instruction a system of rudimental science and manual art. He describes the 

Srogress of industrial education in France, Belgium, Russia, Germany, and Great 
ritain, and the establishment of their professional schools. The technical 
schools of the United States are next reviewed. Mr. MacArthur is anxious that 
the State governments should take up the subject, and enable every girl and boy 
to receive a practical education which would fit them for use in this world. This 
valuable book should be carefully read and meditated upon. The discussion is 
of high importance."— PAitode/jj^ia Fublic Ledger. 

"The importance of this book can not be too greatly urged. It gives a 
statistical account of the industries of various countries, the number of workmen 
and workwomen, and the degree of perfection attained. America is behind in 
native production, and, when we read of the importation of foreign workmen in 
simple manufacture such as glass, it is a stimulus for young men to train them- 
selves early as is done in foreign countries. The necessity of training-schools 
and the value and dignity of trades are made evident in this work. It is particu- 
larly helpful to women, as it mentions the variety of employments which they 
can practice, and gives the success already reached by them. It serves as a hiS' 
tory and encyclopaedia of facts relating to industries, and is very wfell written."— 
Boston Globe. 

"The advocates of industrial education in schools will find a very complete 
manual of the whole subject in Mr. MacArthur's hook..''''— Springjield Bepublican. 

"A sensible and much-needed plea for the establishment of schools for indus- 
try by the state, supported by the practical illustration of what has been accom- 
plished for the good of the state by such schools in foreign countries. Great 
Britain has never regretted the step she took when, recognizing at the Crystal 
Palace Exhibition her inferiority in industrial art-work, she at once established 
the South Kensington Museum, with its annexed art-schools, at a cost of six mill- 
ion dollars."- The Critic. 

"The aim of the book is succinctly stated, as it ought to be, in the preface : 
•What is industrial education ? What are its merits and objects, and, above all, 
what power does it possess of ministering to some useful purpose in the practical 
arts of life? ' These are questions about which we are deeply concerned in this 
country, and the author has essayed to answer them, not by an abstract discus- 
sion of technical instruction, but by giving a full and accurate account of the 
experiments in industrial training which have been actually and successfully 
carried out in Europe."— iVe^^ York Sun. 

"A most interesting and suggestive work on a matter of immediate and 
universal importance."— iV^w York Daily Graphic. 

"An admirable book on a much-neglected subject. Those countries have 
made the most rapid advance in the line of new industries which have paid the 
most attention to the methods here recommended of primary instruction. The 
land that neglects them will sooner or later cease to be in the front ranks of 
applied science and the useful arts." — New York Journal of Commerce. 



For sale by all booksellers ; or sent by mail, post-paid, on receipt of price. 



New York: D. APPLETON & CO.. 1. 3. & 5 Bond Street. 



SULLY'S TWO GREAT WORKS. 



Outlines of Psychology, with Special Reference 
to the Theory of Education. 

A Text-Book for Colleges. By James Sully, A.M., Ex- 
aminer for tlie Moral Sciences Tripos in the University of 
Cambridge, etc., etc- 

" A book that has been long wanted by aU who are engaged in the 
business of teaching and desire to master its principles. In the first 
place, it is an elaborate treatise on the human mind, of independent 
merit as representing the latest and best work of all schools of psycho- 
iogical inquiry. But of equal importance, and what will be prized as a 
new and most desirable feature of a work on mental science, are the 
educational applications that are made throughout in separate text and 
type, so that, with the explication of mental phenomena, there comes at 
once the application to the art of education." 

Crown 8vo. Price, $3.00. 



Teacher's Hand-Book of Psychology. 

On the Basis of "Outlines of Psychology." By James 
Sully, M. A. 

A practical exposition of the elements of Mental Science, with spe- 
cial applications to the Art of Teaching, designed for the use of Schools, 
Teachers, Reading Circles, and Students generally. This book is not a 
mere abridgment of the author's "Outlines," but has been mainly re- 
written for a more direct educational purpose, and is essentially a new 
work. It has been heretofore announced as " Elements of Psychology." 

NOTE. — No American abridgments or editions of Mr. Sully'' s works 
ire authorized except those published by the undersigned. 

12mo, 414 pages. Price, $1.50. 

D. APPLETON & CO., Publishebs, 
New York, Boston, Chicago, Atlanta, San Francisco. 



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